Hi Catherine -
Welcome to the forum.
I leave questions about which pass to buy to the experts - the forum moderators Arno and Annika. They know everything about them. ;-)
Regarding Zürich - I love the town. It is normally not the first choice for tourists. However, I always stay there a few days when I am in Switzerland and walk in the old town (both sides of the river) and explore the museums, churches, stores, and walk in the parks along the banks of the lake on either side.
The walks may be a bit cold in early February, however. And, they might not fill a day. However, it gets dark early in winter.
In another rather long thread I posted some maps of interesting areas in Zürich for walking.
Scroll down that thread and you will find some maps, as well as discussions of Zürich, the public transport network, and surrounding areas.
You will also find links to maps and rail timetables, as well as this link:
You can walk easily to many attractions in Zürich.
However, the trams and buses are very convenient. Since the town has hilly areas, a tram ride is sometimes welcome. Also, on a cold day. Note the discussion in the thread I linked to above. A Swiss Travel Pass (if you choose that pass) will include free travel on the Zürich public transport network. Or, you can buy a day card or a "24 hour card." or others. That is why I pointed to the office of the "ZVV" in that thread. ZVV is Zürich Verkehrs Verein - Zurich transport Association. You can get a map of the tram network.
That said, many first time visitors find that Luzern is a better city to visit for a quick trip. It is discussed and linked in that thread above. Also, here:
Luzern can be accessed by trains to/from Zürich at least twice per hour which take about 45 minutes.
In both Zürich and Luzern, the tourist information offices in the main train stations are very helpful with suggestions. In Luzern, it is by track #1.
I'd suggest that you give serious thought to Luzern, rather than Zürich.
Have a great trip.