Re: 3 months turist permission expired after how long I can come back to Zurich
EU citizens don't need permission to come here as tourists. Theoretically you have 3 months and then if you want to stay longer you're supposed to register as being a resident of Switzerland, ideally with a job all ready to begin or be independently wealthy enough that you don't need to work. Or as a job seeker, but you must have the financial resources to be able to support yourself while you job hunt. But as Plumtree has pointed out, there are no border controls so it's impossible to check on EU nationals crossing the border.
Non-EU nationals are of course checked at the Swiss border so after 90 days they have to leave the country and can't come back for another 90 days.