Unless the Rotom in question has Toxic it isn't getting past Zapdos anytime soon as Zapdos can Pressure-stall it easily. Just stick a Tyranitar in your team, what I always do, or smack status on it.
I'm having serious trouble with Zapdos, Aquilae. It's been taking out basically my whole team, and I wanted to know which Rotom form'd make a good counter to it.
I've been using Sub Kingdra. Mainly because I'm getting completely pissed off at things like Cress coming in and tanking whatever I throw at it and T-Waving me. Sub lets it screw up ALL of Garchomp's counters (Suicune, Cresselia, Cloyster, etc...) It also makes it unable to be revenged easy by (the growing-in-popularity) ScarfMence.
Anyways have you tried DDKingdra with Yawn? In theory it would mess up most if not all of its "counters", but I don't know what exactly counters DDKingdra outside of Celebi / Shaymin both of which have NC.
WHAT'S UP AQUI HOW YOU DOING TODAY
89% IS WHAT I'M GONNA PAY
SAY HELLO TO GATR HE'S IN THE BACK SEAT
GATR: YO GIVE ME SOMETHING BIG
WITH A BUNCH OF BEEF