For fondue, check out Swiss Chuchi or Frau Gerolds Garten.
For treats, Conditorei Schober is a lovely historic cafe.
My favorite market in Zürich is probably the Markthalle Im Viadukt - wonderful food, a great cheese shop (Tritt Käse), as well as some fashion shops. And one tram stop away from this market is Wurst & Moritz, a little fast food outlet which is one of my favorite places in town to grab a plate of wurst and some french fries.