The route from Milano to Zermatt does pass through the Simplon tunnel, and several other tunnels, however there is quite a bit of scenery to be enjoyed too. The majority of the line is in open air.
Route is Milano to Visp, where you change trains.
The 40 minute ride from Visp to Zermatt takes you through some stunning scenery. You travel up the valley with the river right below as the railway snakes its way upwards.
Once you get to Zermatt you might like to take the other train to Gornergrat from where you can get fabulous views of the Matterhorn. The station for Gornergrat is right opposite the Zermatt main station.
I loved this journey when I went on it last January. I want to return now in the summer months.
Have a great trip,
There are various tunnels and some good scenery in between as well, like in most of the scenic european trainrides !
The Trains and buses are in General the best solution for travelling in Switzerland !