Given that the deadline for filing the tax return or for extending the deadline is approaching (March 31), I thought this great thread deserves all the boosts it can get.
Here is the address for the extension if you live in Zurich:
https://e-gov.stzh.ch/efristen/servlet/FSIServlet
You just have to fill in some numbers from your tax form and choose how long you want the extension to be.