The best ticket to get for your arrival day is the "Saver Day Pass". This is a discounted day pass that gives you unlimited travel on all public transit in Switzerland. So that will get you to Interlaken, or wherever it is you intend to stay.
However this pass must be bought in advance, and gets more expensive the longer you wait. So buy it as soon as you have booked your flights:
So go to www.sbb.ch, search for "Zurich Airport" to Interlaken, and you will usually see it as one of the offers.
The other offers will be:
-- Point to Point ticket. Also fully flexible, but only valid on the route you bought. Is refundable until the day before travel.
- Supersaver ticket: Cheaper. Not refundable. Not flexible. Avoid if you are arriving by air. If a delayed flight makes you miss your train you will need a new ticket.