I only Z-mass I used was Cyclo Z-mass and that stuff worked great. Tastes like crap, but it works. I've also used ZMA HP from EAS. I like it the best because of the N-Acetlycysteine (NAC). Most ZMA products are going to have the same zinc and magnesium in it; this is produced by SNAC Systems and is distributed to a lot of the supplement companies. What's different about each product is the extra stuff (vitamin B, vitamin C, etc). Just be sure to choose a reputable brand.
-------------- --JBennett "I've up-ed my intensity.... now up yours!" "Pain is only weakness leaving the body."