Please help me verify Zur, Eternal Schemer's ability

I'm having trouble finding an answer in the rulings, and would appreciate any help. I'm trying to put together an EDH deck using [[Zur, Eternal Schemer]] as the commander. Let's say I have Zur out, along with a god like [[Athreos, God of Passage]]. My devotion to white and black is less than seven, so Athreos isn't a creature. Am I allowed to turn Athreos into a creature anyways, using Zur's activated ability? If I do, does it become a 3/3 instead of a 5/4?