You don't need Diamond Storm to keep Stealth Rock up against Zapdos actually.Yeah, that's pretty much the go to set, though if you're really Mawile weak, I'd get rid of protect. Diamond storm is needed to threaten Zapdos and prevent it from getting rid of your rocks. Protect is great for scouting, but it can also drain momentum (e.g that lando you used protect on is actually double dance).
252 SpA Diancie-Mega Moonblast vs. 248 HP / 0 SpD Zapdos: 198-234 (51.6 - 61%) -- 94.9% chance to 2HKO after Leftovers recovery
From my experience, Diamond Storm is the easiest move to drop for Earth Power.