Speedplay if you want to wear road shoes, otherwise ATACs.
I've haven't ridden the Zeros, but I put a lot of miles on the good old X pedals. They're great if you are into a ton of float. Easy in/out and I never felt like i was going to accidentally clip out. The downside to the speedplays are off of the bike. The cleat is all metal and slippery on cement. I hate the fact that they mount with philips screws and not hex, but that's a personal preference.
I'm running ATAC XEs now. I think they are just about perfect. Easy in/out. Float for my lazy right leg, and they feel really secure.