
The image of a decayed Jesus corpse emerging from a tomb to munch on the brains of believers really is a great metaphor in many respects. You've got the fun observation that if Jesus really did come back from the dead, this would make him a zombie. You've got the munching of brains as saying something about how Christianity (and faith in general) afflicts the mind. You have the spread of the zombie virus from person-to-person and the similarities it bears to the viral nature of religious belief. You have the highly resourceful nature of the holdouts - small groups of uninfected survivors banding together to oppose the infected hordes. You get the idea.
Some will protest that celebrating Zombie Jesus Weekend amounts to little more than mockery of the Christian faith. It certainly does have that aspect to it, but I do not think it has to be so limited. And besides, there may be some value to poking fun of absurd beliefs from time to time.