Everything was going really well until I changed the location of the training as well as her position from lying to standing. She indicated that she wasn't doing so well in this new scenario.
It's my responsibility as teacher to listen to her and modify the plan if she is having trouble with it. Training should be fun for both of us. If the fun-factor disappears, I need to get it back as quickly as possible. If I don't, at best, reaching my teaching goals will be slow, inefficient and devoid of enthusiasm on the part of my pupil. At worst, Zuri may develop a dislike of the particular training task leading to avoidance or escape and even fear of the muzzle when it is presented.
So what did I do? I stopped trying to make her move whilst wearing the muzzle. All she had to do was stand for a few seconds with it on and I fed her. Back to how we began on the bed. I then kept it on for longer and longer before I asked her to move. When I did ask for movement, I chose a task she knew really well and enjoyed: Touch. She didn't have to move her body, just her head so her nose touched the palm of my hand. Very quickly this transitioned to her being able to move a step to touch and then follow me a few steps to touch without showing signs of discomfort. Soon she was spinning when asked and even of her own accord!
And now for my unfortunate analogy: https://youtu.be/Vp85lVTgTFo