In an alternate universe, Dr Zomby is a virologist. He captures zombies and performs viral experiments on them. Dr Zomby once saw a presentation on what would be required to make fire breathing dragons real. Intrigued, Dr Zomby captures some sturdy young zombies, and begins experimenting on some viruses and injecting them into the young walking dead. The virus makes the skin of the young zombies rough and scaly. They begin to take on the appearance of lizard men.
Next Dr Zomby introduces viruses that incorporate exotic platinum compounds into the cells of the young zombies. After many failures and many dead, scaly zombies who puked metal and died, at last Dr Zomby was successful. For reasons known only to the doctor and perhaps satan, Dr Zomby unleashes fire breathing zombies on the world. Hell just got worse.