travel from switzerland to italy

Two days each would be too much moving and too brief in each place for me. I would consider saving Cinque Terre for a future trip and make the most of northern Italy.
Is everything booked? Moving to your farthest destination and working your way back sometimes works out better, but if it's all sorted, then no worries.
I have a heck of a time finding a good source of info on train connections between Switzerland and Italy (surely there is a good webpage somewhere that break this all down!), but someone will come along who knows.

Thank you for your help. I felt like that might be too much moving as well. We really want to go to Cinque Terre, so maybe just best to focus on that.

It's a lot of time on the train, but maybe worth it to you to get some coastal time in contrast to your mountain time. I would stay no fewer than three nights in CT to give you two full days to enjoy the coast, plus to account for the long train trip. Then you could do either the lakes or Milan, as you can day trip to one from the other, it just depends on if you want nature or city.
If your flight out of Zurich is not too early (say around noon), note you can stay in Lucerne the last night, as it is an easy train trip to the Zurich airport from there (if it is not in your itinerary already). That might shave off some of the travel time--always a drag to have to travel extra on your last day!

Since you've said Cinque Terre is a top priority, I'd say go right there from Zermatt and choose one other place to visit on your way back up toward Zurich. Como and Lugano (the latter, of course, on the Swiss side of the border) have good train connections with Milan, IIRC. Then if train connections are such that you have to backtrack into Milan to get an express train to Zurich, you won't be going too far out of your way.

To get to the Cinque Terre is about 7 hours by train. (I agree with the above recommendation that you spend at least 3 nights to make it worth the long trip to the Cinque Terre.) The route is Zermatt to Brig to Milano to Monterosso or La Spezia. From there, you can go to the village of your choice.

I would buy this on www.SBB.ch/en. If you have a pass of some sort (STP, Half Fare Card) it will apply as far as Domodossola in Italy. The lake makes a good additional location. 2 nights in each of three places just seems like too much moving around.

I think your plan is too ambitious, with too many places, given the time constraints and the travel time between these places. And considering that you would need to be back in (or near) Zurich the night before you fly home. If you don't yet have flights booked, consider flying home from Milan, to save the back tracking. If CT is more important, then ,omit Lake Como.