No offense intended bethridg but the actual Audi boxed factory rotors are made by SHW of Germany. Zimmerman is an OE supplier of some brakes to Audi and many other manufacturers but not for the RS6. SHW also produces most of the other RS cars rotors as well as for many Porsche rotors in 2-piece applications.
Zimmermann does make a replacement rotor for the RS6 which appears to be of good quality but they were never a OE supplier to Audi for the RS6 or any other RS application.