Voted Shockproof. It's worth pointing out that by forcing Zapdos to run different spreads or attacks to deal with it, CAP6 can still accomplishing it's purpose in a somewhat roundabout way. If Zapdos runs HP Flying, then it has no effective way of dealing with Swampert, for instance. Part of what has made Zapdos so fiercesome was the coverage it gained following Platinum changes (Heat Wave) and Garchomp being banned (being able to run HP Grass without fear). HP Flying might help him deal with CAP Pokemon in general and a CAP6 w/Shockproof in particular, but it has to give up important coverage to do so, meaning other Pokemon could potentially take it on more easily.