There is a park and ride point at Bahnof Tiefenbrunnen at the south/eastern end of Zurich. I think it's only CHF 5ish for the day. There are two trams that leave from there and then you can get to anywhere.
http://www.rzu.ch/pdfs/pur_zuerich.pdf
On Page 2 of the .pdf there is a map with all the park and ride points in Canton Zurich.