Nice looking frame. Just a few points:
In addition to the Zeus Reynolds and Columbus frames they also used French Durifort and Vitus tubing, at least in the '70s. In fact, I've never seen a Columbus Zeus, but that doesn't mean they dont exist. Some (all?) of the high end Zeus frames in the '70s and '80s were said to be made by the Spanish builder Razesa.
Like many of today's producers, I would bet that the Zeus components on the current Orbeas are the usual contracted out to Taiwan stuff (not that there is anything wrong with that), rather than anything made in-house by Orbea. Compare the Zeus brakes to Tektros.......