Arriving in Z with dog

I have never gotten a USDA stamp before going to Mexico, Europe yes, Mexico no. Current rabies, internal and external parasite test, and a letter stating your pet is healthy, it's easy.
Check out http://jaltembabaylife.com/pet-travel#mexico-pet-regs, has lots of info or Bringfido.com either has all the info you'll need. I usually end up with about 7 pages of stuff from my Vet, but they are extremely thorough about paperwork. Last year there was another woman entering Zihua from the States with a large dog, she had one little piece of paper, looked like it had been in her pocket for a week and they let her in.

They do check when entering in Zihua, I agree, be prepared to be the last one out of customs. Make copies of your forms and have them somewhere safe, they check on the way of the country.