Hi, thanks for joining. A few other things might help. Is CMZ cefmetazole? This isn't an antibiotic we usually see used in rabbits. How long have the rounds of this medicine been?
Are you in the UK, Aus, or NZ? These places have a disease that causes crusty lesions around the eyes and nose that is called myxomatosis, and it's very deadly. If so, please get him back to the vet ASAP.
Another possibility is syphilis. This often appears with crusty lesions around the nose, eyes, and genital area. It's treated with antibiotics, but the typical one used is penicillin, so I don't think CMZ is very effective against it. The vet can usually determine by looking at the rabbit and perhaps other tests if it is syphilis. Don't worry, it doesn't transmit to people, but it will transmit to the other bunnies, so if he's housed with any others they will need to be treated too. This infection can lie dormant and not have any visible symptoms, and they can still pass it to each other without symptoms.
Other options include a different infection of the eye. Many bacteria are resistant to one or more antibiotics. CMZ is a 2nd generation cephalosporin, which isn't very common, so I would be surprised to find that Kyle was infected with a resistant bacterium. Other things can cause infections, such as fungus, and fungal infections of the skin around the mouth are pretty common (at least I've heard of them on the forum here), also causing crusty lesions.
What I would do is take him to a different vet for a second opinion. We have a listing of good vets that have been provided by forum members or rabbit rescue organizations. These vets will know what syphilis looks like and how commonly CMZ is used in rabbits, if the dose is correct, etc.