The official place to go is the Musikkonservatorium Zürich, I would say. The teachers have all the certifications you could want. Here is their list of trumpet teachers: https://www.stadt-zuerich.ch/ssd/de/...ty-zuerichberg
As an alternative, you can go to the Jecklin store near the Kunsthaus. They have a blackboard where musicians post their ads looking for pupils. Maybe, you can also post there.
I would assume that the Musikkonservatorium also has a blackboard, but I don't know where that would be. My guess would be the main building, address is on the website under the above link.