If, as I suspect, Paul based the death and resurrection bits of his cult on Mediterranean vegetation cults, then the eating of the dead King is perfectly natural, as he represents the harvested crop.

As to zombies, the idea originates in Haitian folklore. A dead person reanimated without the soul by a bokor (back magician) as a slave. The story was used to keep slaves on plantations in line by theatening them that they coud be replaced by or made into zombies if they didn't behave.