Black-MZ is basically an American Pioneer Powder product. Alliant does not even make it. Very similar to the other APP powders and Shockeys. I was under the impression its been discontinued and APP is having some problems. Overall it yields pretty poor speed but it ignites easily. Its a very chunky powder, often referred to as kitty litter. Clumps quite often a new bottle. Same patent# as all APP products. patents.google.com/patent/US5557151A/en
If your friend is using a percussion rifle the BlackMZ does have the advantage of being super easy to ignite and cleans up much easier than Pyrodex. Far less corrosive too.
Thanks again. My friend is already using White Hots. So I'm going to advise him to stick with them. He just started muzzle loading and I have been trying to teach him some good safety habits as well, especially when his shooting station is nearby, chuckle.