Jul 19, 2015 - 4:47 PM
Hi Vibeke, thanks for your post!
The Swiss part of your trip basically consists of 4 longer trips and perhaps a few cable car/cogwheel train trips (such as Gornergrat). A 4-day Swiss Travel Pass Flex Combi fits that plan: it includes 4 days of unlimited traveling, and discounts on trips during the non-travel days. The Swiss Half Fare Card is an alternative to consider. If you want to compare them price wise you can do the math as explained here.
An Interrail pass offers less benefits: no free traveling to Zermatt, and less cable cars are discounted. So be sure to check carefully what's included in Switzerland, France and Italy. There may be local passes for France and Italy, but I don't know about those. Regular train and bus tickets are usually not that expensive there, especially in Italy.
The two passes I suggested for Switzerland are cheaper if purchased online (see the linked pages and click "Price"). But I'm afraid it's too late now to purchase them that way. They're for sale in Zurich too.
I hope this helps a bit!