Do you have a Saver Day Pass, or a Supersaver Ticket? Nomenclature is important here.
Supersaver Ticket: You must leave Zurich on the train you booked. If all goes fine you will travel on your booked trains. If you miss a connection (rare) you can take the next train.
Saver Day Pass: You can take any public transport in Switzerland for a whole day. So you are free to take even a an earlier train from Zurich, or take a scenic detour or even go somewhere else completely. A Saver Day Pass is a good option if you arrive by air, as you can just proceed to your final destination at the earliest opportunity after you have landed. You are not limited to the trains you selected during purchase.