Zurich does not give its secrets easily!
Animals in Masoala are free ranging, and some are difficult to see. Some are only representatives of their species in any zoo, like pitta-like ground roller. To get the missing ones, if you see keepers and staff in Masoala, ask in which place in the hall they hang out.
Goodman's mouse lemurs living in the hall are visible about 2 times a year - in midsummer when the zoo night takes place, and in autumn before time change when the zoo closes just before dusk. Otherwise this is a zoo animal which is invisible.
To see elephants underwater, check their bath time, and arrive earlier to get a place.
The zoo has native rescued bats - but visible only once a day when a volunteer feeds and weighs them. The bats are diverse species, not usually seen in zoos, but come and go and are not advertised. Ask at the entrance or go to the bat rescue station at the children zoo, not far from Masoala. Check the actual feeding time, and return then (unless there is a volunteer feeding the bats already).
If you are in Zurich, there is a free aviary with interesting birds in the city park near the lake (Zurich Voliere or Voliere Mythenquai). Outside can be seen all day. Inside is, again, open briefly at inconvenient times. Try checking their website. It is a little place but has unusual birds.
I hope some Zurichers can fill the current details - I was there last 2 years ago.
