Hi kaitlinmh
If you "only" want to travel from Zurich Airport to Zermatt and back, I recommend you to purchase the Swiss Transfer Ticket (CHF 146.00 2nd class / CHF 234.00 1st class).
You may find an overwiev of the offers of the Swiss Travel System on our website.
Those tickets are not restricted to a particular train. They're valid in any train on the selected days of travel.
Kind regards
SandraI