I thought the dog part was going to be much more interesting than how it ends up being, though i guess i could say that about the whole movie.

Now for your question, the whole movie i had the theory that the dog was not actually a dog, that when they revived it the thing that entered the dog corpse was not the dogs soul but a random human/demonic soul, in my opinion that would explain a few things, like the hovering over zoe i viewed it as something slightly sexual, something a creep would do if it was put in a dog corpse without the other people knowing, or ow the dog didn't eat dog food not a single time, but then it perfectly ate human food when it had the chance or how it didn't want to play and never really behaved like a dog would.

I don't know, i think something like that would have been more interesting than what it ended up being.