I realize this is an old thread, but I too was searching for Tempeh and found two sources. I'm in Lausanne, and found tempeh at this store: http://www.magbio.ch/data/magbio/index.html
I'm not sure they deliver to Zurich, but you could call and ask where you could find it in your area. This tempeh is sold in smaller pieces in jars in a liquid...so not sure if it is too fresh, but good enough if you are desperate for it.
I also have ordered it from here: http://futur-natur.ch/Webshop/ws_tempeh.htm
This Tempeh comes in blocks and are vacuum sealed and fresh! Which I liked better. Just make sure you use it right away because the older it gets the harder it is to cut/cook without it falling apart.
Better alternative for you since you can have it sent to you instead of driving to Lausanne.
Hope this helps. If you have any other questions about getting vegetarian/vegan products in Switzerland, feel free to message me. I myself am not vegetarian or vegan, but my wife is. So we have found a lot of methods to vary her diet as it's not as easy as in the US or UK.