Crocodiles of the World (a small UK zoo focussed mainly on crocodilians) has a bridge with two sections of glass floor over their tomistoma exhibit.
Which isn't actually a bridge its a raised walk way that has part of it expanded out over the Thomistoma,so that you can view them through the glass in the floor!
South Lakes has a heck of a lot of bridges (or walk-ways) going through their animal exhibits such as the spectacled bear/tapir enclosure.
Not exactly it, but Zoo Wuppertal has a bridge with a bicycle path crossing over part of the zoo. People biking in the public park bike over an extension of the zoo without being able to get down/in to the zoo (actual gates are elsewhere). From this path one can see lion and tiger exhibits a short distance but away.