Does anyone know a good remote control zap collar? My dog is super dog aggressive and has attacked multiple dogs. We're looking for a collar that we could use on walks to stop her from going crazy at dogs.

You need a behaviorist not a zap collar. The collars can actually make things worse if used with wrong timing.  And if your dog is of a breed known for hearft issues, you can even kill your dog. 

Before doing that, try a muzzle control leash. It wraps around the dog's muzzle and then you attach your lease to that.The pretense is that when you have control of the dog's head.... You have total control of its body too. Helps as a barking deterrent when you tug on the leash too.