Now, to get back to the OP topic. Z-Max is just Critical Defense with a different color polymer tip in the bullet, and loaded in brass cases rather than the nickle plated case of CD. Maybe that's why they were a couple bucks a box cheaper. The bottom line, if you like CD, and oractice with what you carry. You might save a few bucks buying the Z-Max. As long as they keep making it that is. The fad may change, and next year it might be Furry-Max that they come up with!
Cheapshooter's rules of gun ownership #1: NEVER SELL OR TRADE ANYTHING!