I thought that melatonin helped to put your body into a state where you could fall asleep and that ZMA was supposed to help you reach REM faster and with better quality.
There's no 'better quality' REM sleep. REM sleep is REM sleep, and I am unsure as to whether ZMA will get you there faster, but if you get a good nights rest then you wont have to worry about enough REM sleep. Too much is also bad.
I take ZMA when I fail to sleep well. Although I only require 5-7hrs.sleep, by taking ZMA it feels as though I’ve slept for 8-10 hrs.and awake fully rested. In addition, my dreams are wild and vivid in color. Something I don’t experience in normal sleep dreams and not only that but, in my ZMA dreams I see faces of people; whereas, in my normal dreams I do not. Weird.