Hi - our family, 2 adults and 2 teens, will be traveling in Europe this summer. After seeing Salzburg, we will have about 4 days before flying out of Zurich. Our thought was to go from Salzburg to Lucerne and do day trips/touring from there. Are there places we should stop at before staying in Lucerne or are there other places in Switzerland we should split our time between? We plan to take the train if possible.
Lucerne is a very good choice for a 4-night stay. There are plenty of good day trips there!
Many people would argue instead that the Berner Oberland (Interlaken area) is the #1 area of interest in Switzerland, rather than Lucerne, but it will take more time to reach from Salzburg and, since you fly out of Zürich, it will require you to also spend the night in Zürich (whereas you can usually fly out of Zürich while sleeping in Lucerne).
So, even though my initial gut reaction was "go to Interlaken", I do not think it would be the best choice in your case.
Such timing, I was just watching some train videos about the ride from Salzburg to Zurich. Do some digging on Youtube, it's highly recommended. And you get to pass through Lichtenstein so you cross that off your travel bingo card.
Basing yourself in Interlaken does not mean you need to stay the night in Zurich before your flight. It is about 2 hours from Interlaken to Zurich. So depending on when your flight is you can just stay there.
I live in Wengen and will only spend the night before a flight in Zurich if the flight is before 10.