I always love having an opening page for kids to write their name and age. It makes it a keepsake, and I just love seeing their handwriting. I also left a space for them to write their favorite animals.
Each page has a simple color drawing of several animals, with a blank star next to each animal. You can put those shiny star stickers or color them in as you see the animals (or later - I don't think I want to mess with it while we're actually looking).
I left blanks on several pages where kids can draw animals they see that might not be included.
You can download my Zoo Passport. You'll need to print it front and back on letter paper, then cut each page in half, assemble and staple in the middle. Libraries are so great for stuff like this. I rounded the corners of the books to make them more passport-y, too. I'll let you know how our zoo trip goes in a couple of weeks. Any tips for little ones and the zoo?