Upvote:3
According to Timatic, transiting without a visa is possible for Tunisian citizens as follows:
Passengers transiting through Zurich (ZRH) and arriving from a non-Schengen Member State with a confirmed onward ticket for a flight to a third country which is not a Schengen Member State. They must:
stay in the international transit area of the airport, and
have documents required for their next destination.
Changes of onward reservations at the transit station (i.e. once the passenger has arrived in Switzerland) are not allowed.
https://www.timaticweb2.com/integration/external.php?ref=d975cfc59f5c0abd06d16e872198110b