Hi NSJ
In Zurich and greater Zurich area, there is the ZVV fare network. This means, you buy a ticket which includes zones. Zurich is zone 110. Within this zone and ticket validity, you can do as many travels you want with any means of transport (train, tram, buses, boats, funiculars).
If you buy a zone 110 return ticket, you will get a 24-hour day pass valid 24 hours in the chosen zones; again, you can do as many journeys you want. For children, you can buy the same ticket at half fare (½).
But, you do not have to bother with zones. At the ticket vending machine, you simply choose, Zurich HB to Zurich Manegg. The machine will automatically print the correct zones. A normal ticket is CHF 6.20, the half fare 3.10.
The Saver Day Pass / Children Day Pass is also valid for the public transport in Zurich.
Best regards,
Roland