Friend got me curious about it, anyways ZMA is a vitamin and mineral supplement in a correct formulation. basically Zinc, Magnesium, and Vitamin B6.
Basically it's supposed to help you boost your testosterone levels by around 30% in a 8 week study (also boosting libido) and help you get a more sound sleep. and has been used in the past to help provide people with sleeping disorders as well.
Although reading more on the item it's probably more accurate to call say it, helps you to retain your testosterone levels higher longer by avoiding vitamin and mineral deficiency.
Since any hard levels of exercise will quickly deplete your body's level of zinc and magnesium and b6.
All the ingredients are things we'll find in regular multi-vitamins so don't kill me XD
also the content isn't too high. 30 mg of zinc, 450 milligrams of magnesium, 11 milligrams of B6
also the products are very very affordable, like $9 on bodybuilding.com for 30 day supply from Dynatize which is a pretty well known upcoming brand.