Switzerland to Rome, itinerary:

You’ll need to stay at least two nights in Zermatt to give yourselves a full day for visiting and hopefully seeing the mountain. It is notoriously fickle and one can spend several days in Zermatt and never see it. But there are lifts and trains enough to entertain you for a day, hiking from easy to expert. What is more difficult than seeing the mountain is finding a “reasonable” hotel room with a view of the Matterhorn. What is your idea of “reasonable” and have you spent any time with a search tool like Booking.com looking at hotels there?

The Bernina Express does not run from Zermatt, it runs from Chur or St. Moritz to Tirano on the Italian border where you can continue to Lugano in southern Switzerland via bus or stop in Menaggio on Lake Como and stay in Italy.

From Zermatt you can take the Glacier Express all the way to St. Moritz in the eastern part of the country. From there you can go to Tirano via the Bernina Express or regional trains and on into Italy as above by bus or by train to Milan and on to anywhere else in Italy.

Note, the scenic trains are very nice but you can also take regular trains along the same route. Rick Steves has excellent and complete info on the trains and many places you want to go in his guidebooks for Switzerland and Italy. They will help you immeasurably with your planning.

There are direct trains to Visp from Zurich airport at 45 past the odd hour (9:45, 11:45, etc). At other times with a change in Bern. At Visp you connect to the train to Zermatt. Takes 3 1/2 hours to Zermatt.

You can get to Pontresina on the Glacier Express by getting off at Samedan, just before St Moritz, and taking a short connector train to Pontresina. Stay there 2 nights and get the Bernina Express to Tirano, or save the seat reservation fee and take a regular train. From Tirano, walk across the piazza to the Nord train station and take a train to Milan. You might want to stopover 1 or 2 nights in Varenna on Lake Como. From Milan there are direct trains to Monterosso in the Cinque Terre where you can change to local trains to other CT towns.

If you do this, be sure to secure Glacier Express reservations when you plan is finalized. https://www.glacierexpress.ch/en/
Also secure lodging in Varenna.

What time of year and how long do you have?

June 2025. And I have a 6 days between Switzerland with my final destination in Rome late June.

Is that 6 days from landing in Zurich to arrival in Rome?

Yes, airport to Matterhorn to the Bernina train down to Italy cinque terra ending in Rome. Reasonable hotel around $400 under a night. Gather info on sites to see and the name of the trains and stops to get to A-C. From Rome looking for places to stay close by the Vatican and Colosseum.

In which case spend 1 night in Pontresina and 1 night in Varenna or Milan and that will give you 2 nights in the CT.
Train schedules at www.sbb.ch
If this trip is after June 8, the Italian trains may not show up on the schedule yet, but they will when June rolls around.

Thanks, for the comment. So Matterhorn then a train to get over to the Bernina train. Then from there over to Milan? Or the Bernina train to Pontresina then over to Italy down to the cinque terra?

AS this is for June 2025, Reservations will not be open yet, but you can start getting ideas and prices.

Adding to Sam’s suggestions:

Train from Zurich airport to Zermatt, 3.5 hours with one change in Visp or maybe 2, at Bern and Visp

2 nights in Zermatt. For a family of 4, an 2-bedroom apartment would be the best option. You can find them on booking.com. Here are some examples, with prices for a 2-night stay this June: Le Bijou, $693; Eagle Apt., $526; Nevada Duplex apt., $781; Brunnmatt Holiday apt., $570. Those may be non-refundable prices; I did not check. And there may be additional cleaning fees.

For comparison, a quad room at the Zermatt hostel with 4 bunk beds and shared bath is $587 for 2 nights.

Glacier Express train to Pontresina (Sam gave you the directions; you transfer at Samedan). You will take the Bernina Express (or a regional train) to Tirano the next day, and it stops in Pontresina, but not at Samedan. So you can spend the night in either town. We stayed in Samedan at Laagers Hotel Garni and they have a 2-bedroom apartment (but I don’t know if they take one-night bookings). There will be lots more choices in Pontresina—-use booking.com to search.

Next day take the train over Bernina Pass and transfer to the Italian train heading toward Milan. You can overnight on the lake in Varenna, or continue to Milan and overnight there.

Then take the train to Cinque Terre for your last night before Rome. There are direct trains from MIlano Centrale to Monterosso, the northernmost of the 5 CT villages. You can stay there, or transfer to the regional train that stops in all the villages before reaching La Spezia.

To head to Rome, you take a train from La Spezia. Use Trenitalia.com to find the trains and the schedule.

Pontresina would be the start point for the Bernina train. It is near the terminus of the Glacier Express from Zermatt.

What is VISP? The that train from Zurich to Matterhorn?

Visp is the name of the station where you change to trains to Zermatt.
You might benefit from taking a look at the Swiss railway map to get your bearings.
https://www.seat61.com/reference/swiss-train-map.pdf

That nap was very helpful. VSP to Pontresina is it possible to do it in one day or a days trip.

Like I said, Glacier Express to Samedan, then a short train ride to Pontresina. Assuming travel is this summer, 2 direct train a day from Zermatt to Samedan, at 8:52 am and 9:52 am. It will take 8 hours to get to Pontresina.