We've have terrible problems with corrosion and salt on our dodger/bimini zippers. It's probably because we live on the hook and do not wash them after sailing. We lube the zippers and sliders with petroleum jelly frequently and fill the sliders up with the stuff so salt can't get in, on those we do not use often.
We've tried all the lubes and suggested products above (and plenty of others) except the Zippy Cool and none has worked even a little bit, especially the PTEF products which gave us a false sense of success.
Once again, I'm certain our problems stem from constantly sailing without fresh water rinsing them, or using them often enough.