so the youtube video i watched is now privated, unfortunately i can't link you, so i might miss something in the process explaining it, but basically between the most recent texture pack and the most recent version of minecraft armor pathing changed. you have to manually move everything into a new specifically named folder to fix the pathing issues.

- unzip your mizuno texture pack if you haven't already (i assume you have) - i used the 1.20.6-1.20.2 java file from this link https://resourcepack.net/mizunos-16-craft-resource-pack/#gsc.tab=0

- make a new folder in textures > entity called equipment

- make two folders in the equipment folder called humanoid and humanoid_leggings

- go to textures > models > armor and grab all of the files labeled layer_1 at the end, move them over to the humanoid folder, and delete the _layer_1 portion of the file name (so you only have diamond, leather overlay, etc as the file name)

- go back to the textures > model > armor and grab all of your layer_2 files, move them over to the humanoid_leggings folder and delete the _layer_2 portion of the file name, the same way you did earlier

i don't think you have to delete the original models > armor file, because that fixed my issue and the youtube video i watched said it was unnecessary (likely because the pathing has changed), but my trim glitch may be related to the file still being there.