Which ones have you tried? You should be able to price this on either the Italian or the Swiss national rail company website. I think your problem is that your exact dates are more than 60 days in advance. Try different dates to find the price.

www.trenitalia.com (the Italian rail website) shows a special fare (assuming you want overnight trains both ways trip at 115 euros. The Swiss rail website is http://www.sbb.ch/en…

Do you really want to do this by train????

I would say if you can get a cheap berth to do it by the night train but otherwise fly it.
Cheers
Howie

I would route from Zurich through Luzern through Lugano through Milan to Rome, with the same route back. Its about a ten hour ride. Because of the scenery in the mountains, I would not take an overnight train. I would guess the fare (round trip for one) would range from $250 up, depending on whether you can get a discount ticket and what class carriage you want (I’ve always been very comfortable in second class, sitting on the money I save), and whether you get a pass, and a host of other variables. I think it likely there will be a dining car; we often buy the makings of a picnic (most train stations seem to have a grocery or two, and a bakery, in them).