Bedschibaer
NAME = FUCK
That's the thing with the Steelix/Exeggutor core. If it's HP Water Zapdos/Rakiou Exeggutor can just come in, sleep it, hit it with psychics or even explode on it, if it's HP Ice Steelix can come in. The Problem is tho that Steelix has subpar special defense and Rock Slide is not really reliable because of the kinda shacky accuracy. I don't know the exact calcs, but like magic9mushroom said the matchup can go either way, depending on how you play it, depending on damage rolls and most importantly depending on what Zapdos' Sleep Talk picks. Just in case you can alyways go to Snorlax or your own Zapdos on weakened Zap/kou.