OP,
I will venture a guess..I do like OLMO's and they made a lot of bikes some high end and some not so.
The bike pictured needs a lot of work as well as a rehab of the chrome to bring it back to its former glory...crank also looks a bit worn as well. I think with the Group (no campy) and C tubing it is mid to higher end...but the condition is key, in Los Angeles I would say 200 to 300.
Best, Ben

Prices vary from place to place. Your bike appears solid, but nothing really screams BUY ME to a person.

Zeus is a solid groupset, & being unique is nice.

However, quite a bit of rust here and there on the bike and components. You might be able to clean some of it up. The tin foil trick?

If you like the bike, but not the frame size, then you might consider stripping your components and swapping frames. There is a thread... The frame doesn't fit pass-around game

I think you could well get $200 to $300 for just the frame on E-Bay, especially if you put it up as "buy-it-now", and just waited.

Look at other E-Bay listings and sold listings.

The 1980 palmares decal refers to Pier-Mattia Gavazzi's 1980 victory in the Italian Pro Road Race Championships, beating 2nd place Moser and 3rd place Saronni. Gavazzi would be Italian National Champion twice more, in 1982 and 1988, riding Atala and Fanini respectively. His other big win was the 1980 Milan-San Remo Classic, also on an Olmo.

The Italian championships were typically held early to mid season, so it may well be a 1978 model. This is supported by the old style Columbus decal, which was replaced in 1978 but old stock often carried over for a year and sometimes two. It also has the Portcatena dropout introduced in the fall of 1977, to support the age estimate.

Based on the frame size and features, it is almost certainly full Columbus SL. This can be verified by confirming the presence of five helical ridges inside the bottom of the fork's steerer tube. While Zeus components are typically not as desirable or valuable as Campagnolo, the bicycle does have some very desirable components, specifically the Zeus 2000 rear derailleur and 2001 brake calipers, though their condition is only poor to fair. Unfortunately, the other components appear to be lower end Zeus.

Given the mixed components and condition, maximum value will be attained by parting it out. Properly advertised, everything should bring $500-$600. Selling locally, as a complete bicycle, would be about 1/2 that price, in an average market, at this time of year. If you like the components, you could always keep them for installation on a proper size frame. That would minimize any potential loss.