I don't know about Z4M's but I would STRONGLY recommend Shade Tree Garage in Morristown. There is a tech there called Phil Eng and he is great. Very thorough and he knows his stuff. I just had my wife's E46 up there for an inspection prior to the warranty being up. They are honest, fair, and extremely knowledgeable. They have been in business for over 30 years. Class act place. You will not be disappointed.
www.shadetreegarage.com