The train from ZRH to the main city terminal is less than ten minutes and somethink like 8Euro. While there may not be much open yet, it's a very walkable, compact, easy city. In less than 20 mins you can walk down to Lake Zurich if you like. Lots of great side streets, alleys, churches (including the largest clockface in Europe). It's easy to poke around and return to the train station and trip back to ZRH.