cool team, I like how it's structured around cm cress, as those bulky resttalkers basically shit all over today's metagame. but there are a few ways you could improve it. for starters, I'd like you to run a sub/dd/fire punch / eq tyranitar over your current one. withe screens, tar is so bulky that hardly anything can break his subs, and what can usually gets crapped all over by his insanely strong attacks. with him, you lure in scizor, who dies as he breaks your sub. as well as scizor, you also lure in and destroy forry and bronzong, whose explosoins could be harmful to cresselia. and with sub and fire punch, you often get a kill and even then your opponent has no idea what set you're running, so if you don't have an early game run, but just kill scizor, you can really wreck shit later. and of course by the time your screens are out you should have plenty of dds so that your opponent has to sacrifice multiple pokemon to even touch you.
now, with scizor getting lured in and smashed by tyranitar, you usually aren't going to get too much use out of zapdos. you oculd be better off with a gliscor there. max hp, enough speed to hit 309, a tiny bit of defense, maybe like enough to hit 300 and then the rest in attack.what this does basically is allows you to really, well, destroy stuff once mamo is gone (and interestingly enough, cress handles it perfectly). he helps you against sdluke without taking buttloads from espeed before killing the dog, as well as beating down cm rachi should tyranitar be weakened from his early game run. there's also the occasional sand veil miss, which can be cool (or gay, depending on how you look at it) sometimes. he also gives you a backup plan should something weird happen to cress.
other than that, you have a pretty cool team. you cover most of the common threats as well as maintaining a decent enough offense to do your job, and should something happen, you have backup plans. good work.