Campagnolo also used pressed-on steel races on their titanium bottom brackets. These leave less space for the balls, so they need to be smaller to fit everything into the same space. Campagnolo used 3/16" balls; Zeus used 7/32" balls.

Yes they did, but that was a choice. Teledyne and Cobra Brand (Italy) along with another Italian spindle F.?.?. (I forget the name right now) use pressed on steel races too but use 1/4" bearings.
Way back I purchased a set of Italian threaded cups with pressed in steel races (unmarked) that were designed for 1/4" bearings. Very nice, no idea who made them, allegedly Ritchey brand but I use the brand without a box or stampings to prove it.

Apologies if it's socially unacceptable to bring back this 10 year old thread, but is it possible to use a Zeus 2000 Ti spindle (7/32") on Campagnolo alloy cups (3/16")? Which size ball bearings would be adequate?