ZMA is claimed to raise testosterone and IGF-1 levels which may aid in gaining muscle size and strength. While studies have shown that most Americans get enough zinc and Vitamin B6, less than 50% get enough magnesium. BUT!!!
1: its now just zinc and magnesium.( if you go to GNC and just ask them bout ZMA they will throw something like "MHPs T-BOMB" in your face. Price: about $50 for a bottle. And as far as i know its mixed with other stuff like: Tribulus terrestris (the stuff that really increases your testosterone production); Bioperine - Black Pepper Extract ("promotes nutrient absorption"); Flaxseed (again, makes sense since fat increases you testosterone level).
2: It also makes you lose your hair(ONLY IF YOU ARE PRONE TO HAIR LOSS) LOL With extra testosterone in your system, your body converts most of it to DHT a.k.a Dihydrotestosterone (a hormone commonly implicated in male baldness,development of acne, produced from testosterone).
All thou all this sounds very scary if you think about it, in reality its not that bad.
If you are loosing hair then you are most likely to shed while taking ZMA, and if you are not prone to it then you wont lose any hair even if you get on some serious gear. And yes, you will get stronger. So i say give it a try, see how it goes.