This thread could use some Science.....
First off... most of the "Supplements" available do not do what you think they do. Supplements by and large are simply snake oil meant to take your money while giving you the psychologically pleasing feeling of helping yourself. There are some things for sure that actually have affects on your body that make it worth it, as you'll see from the graphic below.
I know there will be many posts saying BS, it worked for me and this guy I know. But generally all these ingredients have been studied to the point that we can prove exactly what it does and doesn't do. If you're convinced it's working for you, then great. That feeling of "Something is making me feel better" is powerful in its own right. Just know that anything labeled "Supplement" has no proof of whatever claim it makes. If there were any proof, it wouldn't need to be labeled as a supplement. And remember that supplements themselves are the least efficient way to introduce those ingredients into your body. Supplements generally are drastically less effective than ingesting actual foods containing those ingredients. Taking a Vitamin C pill is infinitely less effective than eating a couple oranges, etc. Whenever possible, go for the source of whatever ingredient you're wanting.
Here's a very handy graph, showing where the majority of supplements stack up. Note the "Worth it" line. Essentially everything under that isn't worth the money spent on the product. This graphic is dynamically updated and pulls info from the giant table of documentation at the link at the bottom of this post.
Unfortunately, the 3 ingredients in ZMA aren't even over the "Worth it" line.
And here's the link with all the information used to construct this:
https://docs.google.com/spreadsheet/...hl=en_GB#gid=0
That includes links to case studies and actual scientific information from sources that are not trying to sell you what they're recommending.