Michael Levy said " You want Proof ...I got Proof... My team was sponsored by Zeus in the early, mid 80's. I put a Zeus crank set (Campy look alike) on a Colnago Super.....While climbing "Trash Truck" hill the right side crank arm snapped off ! I almost lost my you no whats....."
Searching the CR Archives will retrieve stories/instances of Campaganolo crank arms breaking. So you would be well advised by the experience of others to avoid using Campagnolo cranks as well? Your Zeus experience is a datapoint and doesn't provide definitive "proof" whether Zeus cranks break more or less than Campagnolo cranks.
It's good that the boys survived....
La Jolla California USA