Hi
you phone up the vet of your choice ( if you can, ask friends for recommendations) , set an appointment and get the cat treated. Vets ask for the bill being settled in cash or some with credit card up to a certain amount ( mine's limit is 500.- up of that you can get a bill/paying in slip payable within 30 days)
Vet in German is Tierarzt
This link should take you to a phone directory list i prepped for you listing all Vets in Zurich.
http://tel.search.ch/?misc=Tierarzt&...rich&kanton=ZH