What works for some may not work for others.
I have been taking ZMA for many years. Works for me; Science or not.
3 hours of sleep on ZMA feels better than 6 hours without because I will toss and turn for those 6 hours.
My sleeping ability sucks. ZMA has helped me tremendously.
ZMA is cheap. Try a bottle and see if it works for you. That is the only way you will find out.