@NathanRGMan: Yes, there is an outside exhibit too and it is much, much bigger. The Lions in Zurich spent a lot of there time in the outside enclosure, even in snowy winter days. The zoo staff has tried to bring in free flying Alexander Parrots/Parrakeets in the House, thinking that the birds would be out of the claws of the Lions. Unfortunately, they were not.... Even that try of "joint venture" has failed, there is still a plan that the Lions will get company of Asian Small-clawed Otters (which inhabit an adjected exhibit) in the outside Lion exhibit (corresponding exhibit structures are already built).
You can see part of the outdoor lion exhibit here: http://www.zoochat.com/476/asian-lion-enclosure-zurich-31-08-a-103235/ It's rather nice.
Don't the otters and lions already share the exhibit? I am 95 % sure that they did during my visit this summer. At least I saw the otters indoors alone during the day and outdoors along with the lions in July 2010.
Well, it could be possible (Although I have to say that I have visited Zoo Zurich about 15times during the last 12 months and I have never seem them in the same exhibit at the same time) So maybe you're right or maybe you have seem them together during a test phase which was interrupted for some reason. I will ask and inform as soon as possible.