I have a small (crazy) italian greyhound who is 12, doesn't like dogs, etc...
I always take her to
Helena Frey-Stiftung Tierheim Rumlang.
(
www.tierschutzheim.com / 044 817 2422)
I have never had a problem - the people are kind, there is a sense of calm when you go there (not just the crazed barking of bored, upset dogs).
I toured many places around Zurich and this was, by far, the best that I visited.
It is not too far from Zurich or the airport.
It is a nice small farm (I think it might be an animal rescue).
They board dogs, cats, small animals and maybe birds?
The rooms are big, heated floors, with big windows facing towards a large courtyard. The dogs are usually kept in groups of 2-3 - same size and temperment.
The dogs are let out in smal groups to play in the courtyard a few tims each day. They even dressed my dog in a jacket when it was chilly and I forgot to send her's along!