"Es zapato es nuestro."
Exactly, the sentence in the exercise made no sense to me (it wasn't my sentence). I wrote the answer as "El zapato es nuestro" and they corrected as "Es zapato es nuestro", which made no sense to me. That's why I'm asking if in any possible way, "es zapato" would make sense. But I guess not. Probably just a typo on their corrections.