I have a late-'70s Zeus Professional with the full complement of Zeus components. Around that time the Zeus 2000 stuff was new and the only 2000 components on my bike are the center pull brakes. We ordered some of the 2000 components to have around the shop. I believe the derrailleur was derived from the Criterium (which I have on my bike - which is a mostly steel Campy copy) and had thinner investment cast steel parts, Ti bolts and a drilled-out pulley cage. The 2000 crank was like my Criterium crank with a bunch of holes drilled in the arms and rings (can you say flexy?) and a nice Ti BB. And there were 2000 freewheels made from Ti that were nice to look at, but I'm not sure how long they would last.