the city of Zurich has courts all over town that you can rent for 20chf/hr. No membership needed:
http://www.stadt-zuerich.ch/internet...en/tennis.html (sorry, have not found an english version of the website).
the courts are well maintained and I've never had troubles finding a free court when phoning a few hours in advance. The outside courts close by October 15th, I've heard they have indoor courts too, but haven't found out about these yet.