[gemy]

I was going to not comment again on this thread and then re-considered. First a Boxer as a breed I would not elect to bring into a home with a Yorkie. Boxers are very high energy dogs and always game to play and to play roughly. They take at least three years to settle down and get consistent with their obedience commands.

You have a dog aggressive Yorkie - not a good mix to start out with. I truly believe you need to train your Yorkie and get control and management of her aggression before you think to bring another dog into your home.

You should not start out any puppy with a muzzle. Good grief I have never ever heard of that. If you are not prepared to do the work to keep each dog safe and the training then quite simply just deal with the one you have.