I may not coach basketball, but as a baseball coach and someone who has played all kinds of sports for years, I think it's a combination of things that make Z effective. First, he's fresh out of the league. He's got cred. Also, his height his undeniable and something nearly impossible for another coach to replicate. One of the other things, though, is that sometimes 2 guys will explain/show things in completely different ways. It's not that guy #1 was some horrible coach, but sometimes guy #2's approach/delievery makes more sense. Two guys can preach the same message, but with different words, and it can affect the same people completely different. As coaches, we often attend clinics from HS and College coaches to try and gain perspective and innovative/new ways to teach. It's a very important aspect of coaching. It doesn't necessarily make Mosely or BS bad at what they do that Z can seemingly make a "breakthrough" difference. It just means that sometimes a new voice can deliver the same message in a much more effective way.
Just my 2 cents