SBB offers a Swiss Travel Pass which might suit your needs
With the "Swiss Travel Pass 15 days" you can enjoy 15 consecutive days of unlimited travel on the entire train, postbus and boat network of the Swiss Travel System.
So basically you can use more or less any public transport (also in cities) with this pass, including some mountain railways and a lot of museums. Besides the 8 or 15 days option there is also a more flexible version (Swiss Travel Pass Flex) which allows to travel on 8 or 15 days within a month.
You can actually buy the pass already in advance and print it at home, so you won't need to worry about getting it once you've arrived.
PS: Only constraint is "vailable to persons permanently resident outside Switzerland and the Principality of Liechtenstein"
It really depends on your individual travel plans though, so it might be cheaper to get individual tickets instead (or a Flex Pass for just the few days where you intend to travel a lot). If you already know where you want to go to you can use the timetable information on sbb.ch to learn about the cost of the individual tickets.
In that scenario you also need to consider the price for the pass for the trams, trains and busses within the city of Zurich (CHF 85 for a monthly pass, about 50 for six day passes).