This trip is terribly rushed. More than 1 one-night stop in 22 days is absolutely ridiculous. You’re going to arrive in Vienna or Berlin at 2:00 in the afternoon, only to leave at 10:00 the next morning? It’s possible you won’t hit the open hours for a single museum on these 1 day stops. Skip any place where you only intend to stay 1 day — with the possible exception of Venice, which at least comes close to being a reasonable 1 day visit. If Rome is a must see, then spend a minimum of 3 days there. 4 would be better.

Getting to Zagreb is going to take some time. Is there a specific reason for Zagreb as opposed to the Croatian coast? Zagreb is a nice city, but, IMO it’s not the reason you’d go to Croatia. You’d overnight ferry to Croatia and then spend nearly a full day just getting to Zagreb. If you want to visit Rome and Zagreb in 22 days, then limit your trip to Italy (drop Milan and add Florence, given your interests), Croatia (add Split, Dubrovnik or other coastal, lake areas), a single 2 or 3 day stop on the way to Italy and one stop on the way home from Croatia.