We have multiple official languages, including an Italian derivative and French. Our history is as independently rich, tracing to the Holy Roman Empire, as that of the Germanic tribes.
Yes, but 'German' or 'Germanic' is still the accepted English word to refer to the shared culture and history of all German-speaking areas, of which northern Switzerland and Zurich are definitely part.
The term is not restricted to only refer to modern Germany (which didn't even exist as a unified state until the late 19th century).
I wouldn't recommend calling them German. :)