Wow. Tough one for me. Not only challenged my hip mobility and shoulder mobility, I simply could not coordinate the windmill motion with my left arm overhead. I was surprised.
Looks like the demo achieves one full rotation of the dumbbell with combo of shoulder rotation and forearm rotation. That's tough as well.
I scaled the movement on the first day and did it from my knees. I know it's not the same as standing and as I am able to, I will move to my feet. For now tho, since I cannot preform the movement on the left, I feel equal development on both sides is important and will occur by doing the exercise on both sides from my knees