It stands for nothing in particular. Z06 is just another RPO number. Just like MN6, Z51, etc. It was offered originally in the 1963 version and reborn in the 2001. The "Z" doesn't honor Zora Arkus or anything else. It's just a code that identifies an option. In 2001 it became a "model" designation. Much like today's version, the original was offered as a "factory built race car".