I've got a fair number of pamphlets, guides, books, leaflets, etc from almost 40 different zoos, aquariums and wildlife parks. Every time I visit a zoo I take away two maps, and if possible purchase a guide book as well.
The 4 really old guides that I own:
1- London Zoo guide from 1971, with a two page map enclosed. There is a highlighted section in the middle of the zoo (attached to the monkey house) that is going to be a new primate house.
2- A Taronga Zoo guide from 1972 that talks all about the 1967 master plan and its changes such as the new koala exhibit. There is a two page map that naturally has all the carnivores together, ungulates together, bears together, and even the flightless birds (ostrich, emu, rhea and cassowary) in one section of the zoo. How things have changed!
3- A "Lions of Longleat" guide from 1967, advertising the new hippo and man-ape islands that have recently opened in that British park.
4- A guide from Carl Hagenbeck's Tierpark that is completely in German and doesn't have a copyright date. It appears to be 1950 or even earlier...and it's too bad that I can't read barely a word of it.
I also have a guide to Edmonton's now defunct Polar Park, guide/book from Taronga from 1980, and lots of big books: San Diego Zoo, San Diego Wild Animal Park, National Zoo in Washington D.C., a history of the 5 New York zoos/aquariums, the Vancouver Aquarium...and a huge hardcover book that is the best of the lot and from the Calgary Zoo.