Hope your cat is OK...
I know this is too late for you, but as an FYI for anyone with an off hours emergency in the greater Zürich area:
If you can't get hold of your regular vet or his/her cover vet, as Blowfish mentions, call the
Tierspital (University of Zürich Klinik für Kleintiermedizin). Although they don't keep regular clinic hours evenings and weekends, they are always available in an emergency. If you can't call, and if it
really is a life or death situation, just go to the clinic - there is an intercom at the front door to page the on call vet.
Winterthurerstrasse 260
CH-8057 Zürich
Tel: +41 (044) 635 81 11
When you call after hours, you will get a recording telling you to first contact your usual vet, but keep listening - the recording will also tell you which key to press to be connected to the on-call vet for emergencies. Generally the person who answers the phone after hours is a vet, not a receptionist, and will speak some English. (Actually, most vets at the Tierspital are fluent in several languages.)
There is an out of hours charge added to the regular fees, and one is supposed to pay when picking up your pet. However, each time I've been there for a post midnight emergency no clerical staff were on hand to process payments so they just sent me an invoice later.
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And, taken from the Tierschutz website, here are some emergency clinics in other areas:
http://www.tierschutz.ch/cms/de/adre...notfaelle.html