At a sea-level track, MIR, I ran against a Z06 with 2K miles on his engine. He had DR's on; cut a 1.8 60 ft time and an 11.9 second run. He said he can cut 1.6's with a little practice ... it was a new car for him.
I have no doubt that even on street tires, a person could get a 12.2-12.4 without much difficulty.
I think you are comparing apples to oranges though. You are comparing a sports car (Z06) to a luxury coupe that is sporty (M3). I don't care what BMW says, it is NOT a sports coupe .. it is a luxury coupe that is sporty (IMO). A sports coupe is a GT2, a 996 C4S, Z06, etc.