While I am not a lawyer and possibly may be wrong, I regard what is said in mosques, churches, synagogues etc as "public" as the congregation present is not limited to "members" . The legal problem of course may be what material is allowed in court. But to make recordings for information purposes is not illegal if you are present in person. I however do not believe that any federal service in such things would be in charge, but that it clearly is a matter for the Cantonal police forces. And the Cantonal Police of Zurich has a number of interpreters for Albanian, Bosnian, Turkish and Arabic, who happen to be Muslim by majority. So that some "problems" mentioned simply are irrelevent.