There are many ways of going from Chamonix to Zermatt. Most English speakers follow the route described by Kev Reynolds, but that book describes a few variations. The two Swiss publications, the slim VALRANDO brochure and the book by Bernhard Rudolf Banzhaf, describe several other variations. Finally, looking at the map suggested still more possibilities. I will describe the various major options; many more minor variations are possible.
Trient or La Forclaz to Champex
The two routes from Trient (or La Forclaz) are very different. The high road goes over the high Fenêtre d'Arpette (2,665 meters), with a strenuous ascent and a steep and rocky descent. The low road goes over a ridge at around 2,000 meters.
View Trient-Champex in a larger map
As a result the Fenêtre d'Arpette route is more scenic but also more strenuous. It is also not advisable to use it in bad weather. In 2008 we were advised not to use it after an evening storm followed by a cold night, for fear of icing.
Champex to Cabane de Prafleuri
The area where the routes differ most is between Champex and the Col de Louvie. The (interactive) Google Map below compares three routes: Kev Reynold's route (in red), the VALRANDO route (in blue) and the route I took (in black).
View Haute Route from Champex to Prafleuri in a larger map
Three possible routes: Kev Reynolds (red), VALRANDO (blue) and my "compromise" (black)
In what follows I am assuming that the reader has access to the Reynolds book (almost all English speaking walkers seem to use it), the free VALRANDO brochure and one of the appropriate (282, 282T, 5003 or 5027T) maps.
Reynolds chose a low elevation northern approach, getting very close to the Rhône valley at Sembrancher, then climbing up to the Cabane du Mont Fort, attempting to avoid the worse of the ski slopes near Verbier. From there his two suggested routes go to the Col de Louvie and on to the Cabane de Prafleuri.
I believe that most readers of his book want to go all the way from Chamonix to Zermatt in a single trip during a two week holiday, and for them it may well be the only way. Some people, such as I, plan to do it over two or more trips, and for them there are other options.
The Swiss Routes
The two Swiss publications both chose much more southerly routes, with passes at substantially higher elevations. The VALRANDO route actually crosses over into Italy by the Col de Fenêtre, returning to Switzerland by the Col du Grand Saint-Bernard. Banzhaf's route is only slightly more northerly, crossing into the Val d'Entremont by the Col du Bastillon. Both routes then descend to the valley at Bourg-St-Pierre. From there they climb up to the Col de Mille, and after passing the Cabane Brunet go to the Cabane FXB-Panossière. From there they loop south to different degrees before heading to the Cabane de Louvie, from which they rejoin the Reynolds route before the Col de Louvie.
Since I planned to do the route over a few trips I saw no need to go down into the valley as Reynolds' route does. On the other hand I feel that the two Swiss routes go too far south for what I consider to be a traverse. My compromise is to cross over from the Val Ferret to the Val d'Entremont by a more northerly pass. I had initially favored a route leaving Praz-de-Fort, crossing the ridge at La Tèjere and descending to Liddes. Finding absolutely nothing about it either in print or on the web I decided to follow the Tour du St-Bernard route. This leaves from La Fouly, crosses the ridge at Le Basset, and descends to Liddes. From Liddes I went over the Col de Mille to the Cabane Brunet, from which I went directly to the Cabane de Louvie, rejoining the Swiss routes.
From Prafleuri to the Val d'Hérens
The standard route is to go from the Cabane de Prafleuri directly to either of the two passes (Col de Riedmatten or Pas de Chèvres), then descend to Arolla for the night. Next day take an interesting trail above the valley to the Lac Bleu, then descend to La Gouille and follow the old road to Les Haudères. A variant is to detour to the Cabane des Dix, with its spectacular views, and then cross the remains of the Glacier de Cheilon to the cols and Arolla. With this variant there is the option of spending a night at the Cabane. The standard route and its variant are shown in red on the map below.
View Prafleuri-Herens in a larger map
The third edition of Reynolds' book suggested a variant (dropped in the fourth edition) for those spending a night at the Cabane des Dix. After crossing the col descend about half way to Arolla, then take a farm road to the delightful Remointse de Pra Gra and from there follow the trail to the Cabane des Aiguilles Rouges. This Cabane has wonderful views, both of the icy peaks to the south and the rock wall that separates the Val d'Arolla from the Val de Ferpècle. Next day descend to the Lac Bleu and follow the standard route to Les Haudères. The detour is shown in black on the map.
An alternative that I have never seen discussed, but that I enjoyed immensely on my 2008 trip, uses the high (3,181 meters) Col des Ignes. This route is shown in blue on the map. From the Cabane des Dix cross the glacier, then go north for about half a kilometer, and cross the col to reach the Cabane des Aiguilles Rouges. Zooming in on the map, by clicking where the blue line leaves the red one, will show the start of this route in more detail. It is also possible to go from the Cabane de Prafleuri to the Cabane des Aiguilles Rouges in a single, very long, day. I have not attempted it!
Where to spend the night?
Reynolds suggests spending the night in La Sage, a tiny village above the valley about an hour's walk from Les Haudères. This obviously saves some time next day. You may well prefer to stay in one of the two large valley villages, Les Haudères or Evolène. They have a much bigger choice of both food and lodging. Next day you may walk to the start or, if you are not an absolute purist, use the bus. Inquire about the bus schedule (fewer and later buses on weekends) before making plans.
Val d'Hérens to Val d'Anniviers
The southern route (in red on map), over the Col du Tsaté, is the more demanding route. After going over the col and descending to the valley it crosses the outflow of the glacier, and goes south ascending to the Cabane de Moiry. This high (2,825 meters) hut has spectacular views of the glacier and its icefall, as well as of the surrounding mountains.
View Herens to Anniviers in a larger map
Next day you retrace your steps to the bottom of the glacier, then follow a path above the lake, at around 2,500 meters. At the head of the lake a path comes up from the dam (used by the alternate route) and then both go over the Col de Sorebois through pleasant pastures. The descent is less pleasant, as it is through a ski area. The distant views, though, compensate. There is a restaurant at the upper station of the cable car, where I had a very satisfying lunch. I decided to take the cable car down to avoid what Reynolds describes as a "knee-jarring descent". Purists may well wish to jar their knees on the descent to Zinal!
The alternative pass is the Col de Torrent (first day route shown in black). I did not go over the col, just up and back from Evolène in 2005, and enjoyed the immense Alp Cotter very much. The route then reaches the valley at the dam, where there is lodging at the Chalet du Glacier. Next day a short climb rejoins the route coming from the Cabane, and ascends as described above to the Col de Sorebois.
From there one may descend (on foot or by cable car) directly to Zinal. Since this route is quite a bit shorter than the one coming from the Cabane de Moiry Reynolds suggested (in the third edition, removed in fourth) following a path above the valley to the Cabane du Petit Mountet, and going to Zinal from there (in blue on the map). The views going to the Cabane are spectacular! It is also possible to stay at the Cabane, going to the Hotel Weisshorn next day (this is the route suggested in the VALRANDO brochure).
As an alternative to staying at the Chalet du Barrage near the dam it is possible to go (walking or by bus) to Grimentz, a large village in the valley. Some may wish to go there for the greater choice of accommodation, these will return to the dam (almost certainly by bus) next day and resume the itinerary described above. Reynolds suggests several alternatives for those staying in Grimentz; in my opinion the only really logical one is to go next day to the Hotel Weisshorn.
Val d'Anniviers to Turtmanntal
There are two passes between the French-speaking Val d'Anniviers and the German-speaking Turtmanntal, the Meidipass to the north (blue placemark on map) and the Forcletta to the south (red placemark). From Zinal it is quite easy to go over in a day, while those spending a night in Grimentz or at the Petit Mountet hut will need to spend another night at the Hotel Weisshorn or the Bella Tolla hut. Almost everyone goes to Gruben in the Turtmanntal, though Banzhaf suggests a detour to spend the night at the Turtmann hut.
View Anniviers to Turtmanntal in a larger map
Reynolds' standard route goes from Zinal over the Forcletta to Gruben, a route that is both direct and scenic. From Zinal he suggests two variations, going further north high up in the Val d'Anniviers to ether the Hotel Weisshorn or, in the fourth edition, to the Bella Tolla hut. This is a very scenic route, but unfortunately you have to turn around to see the best views. Next day go over the Meidipass to Gruben.
Those spending the night in Grimentz will go to either the Hotel Weisshorn or the Bella Tolla hut, next day going over the Meidipass to Gruben. Those spending the night at the Petit Mountet hut (the VALRANDO route) will hike to the Hotel Weisshorn high above Zinal, a delightful scenic hike with the only problem being that you have to stop and turn around for the best views.
Turtmanntal to Zermatt
There is only one pass between the Turtmanntal and the Mattertal, the Augustbordpass. The main route from Gruben goes directly to the pass, after about a kilometer the route from the Turtmannhütte joins it. The final descent from Jungu to St. Niklaus is very steep; I chose to take the cable car down. I had a long wait as the cable car does not operate between 11:00 and 13:00, lunch time!
View Gruben to Zermatt in a larger map
There are two very different routes between St. Niklaus and Zermatt. The valley route more or less follows the road and river, it is flat, easy and of limited interest. The newer Europaweg is the exact opposite: lots of ascent, rough terrain and spectacular views. It requires two days as opposed to one for the valley route, with a night spent midway at the Europahütte. It crosses two or three areas of active rockfall where caution, and speed, are required.
Those taking the Europaweg have a dilema, unless they are very fit. That route starts at Gasenried, 1:40 above St. Niklaus according to Reynolds. It is a lot to add at the end of the long trek from Gruben to St. Niklaus, and also a lot to add at the start of the equally long trek from Gasenried to the Europahütte. So Reynolds suggests devoting an extra day for it. Unless you are a total purist I would strongly recommend taking the bus, either the afternoon you arrive in St. Niklaus, or early next morning.