You can use the European train websites to help you make choices about your route and where you will stop along the way. For this purpose I find the Swiss rail site www.rail.ch the simplest to use.
Let's say you decide to go to the Berner Oberland in Switzerland, instead of Zurich. If you put in Amsterdam and Interlaken Ost as your starting and ending points, it will show you that the most direct route is via Frankfurt; you can do the trip with only one train change.
To compare to a route with a stop in Paris, put Paris in the "via" block. You'll see that the trip via Paris is only slightly longer. Click on "show intermediate stops) to see the towns you will pass through along the way. going this way, you could choose to stop for a night in Strasbourg or Mulhouse. Or you could decide you want to spend more time in Switzerland, and continue straight to there. (It is only 5.5 hours from Paris to Interlaken Ost). But don't stay in Interlaken---continue the short distance to Lauterbrunnen and then on up to oe of the car-free villages perched high above the valley for beautiful scenery (and great food, at least in Wengen).
Another good choice in Switzerland would be Luzern, a lovely town on a lake, with nearby mountains you can visit by boat. cogswheel train and cablecar. Rigi is especially nice in June when the flowers are blooming.
From either the Berner Oberland or Luzern it is an easy trip to Milan to begin the Italian portion of your trip. 5.5 hours or so from Interlaken Ost; about 4 or 4.5 from Luzern.