Hi,
Welcome to the forum. Instead of a package I'd suggest plan your trip.
4 days is an ample time to go anywhere and Zurich being in the centre, it helps
Plan-1
1. Day 1: You can rent a car in Zurich and drive up to Milan (3.5hours). Start early and enjoy the rest of the day roaming around Duomo etc. Book a hotel in advance for the night.
2. Day 2: Check out and drive to Venice. Another 3 hours and enjoy the city. Spend the night there.
3. Day 3: Drive up to Florence and Pisa. Spend the day and night.
4. Day 4: Drive back to Venice (takes around 3hours from Pisa) and from there back to Zurich (5 hours).
Plan-2
1. Day-1: Travel to Innsbrucke, on a train reservation. 4 hours. Start early and spend the day at the Swarovski Museum.
2. Day-2: Go to top of Innsbrucke and explore the rest of the city. Evening take a train to Vienna (4hours). Recharge your batteries.
3. Day-3: Explore the city of Vienna.
4. Day-4: Make a halt at Salzburg, (2.5hrs from Vienna) the birthplace of Mozart. Explore the city. Take a late evening train back to Zurich via Innsbruck.
Plan-3
1. Day-1: Travel to Munich. Start early. Explore the city and spend the day drinking beer and tasting the local food.
2. Day-2: Travel to Nuremberg. Explore the city.
3. Day-3: Travel to Prague. Go nuts.
4. Day-4: Return
The key is ensuring you have all your itinerary clear in your head and your reservations done well in advance. A baby might need additional care and some modifications but this is basically a rough idea.
Have a nice long holiday weekend.
PS: the prices might be a tad higher everywhere. Try AirBnB.
PS: Double Check everything.