Hi, what website has information on renting a market stall for a christmas market in winterthur or zurich ?

Maybe you can find the info here.

That website was where I got a lot of info about the various markets. A lot of smaller communities or villages also have Advent or Christmas markets. You really need to check out the individual websites of different communities where you might want to try getting a stand. As for the larger markets (listed on that website), if you are looking for something for this year, you're probably out of luck. The deadline for applications can be as early as June. It's still worth it to try, because there are sometimes cancellations.