Unless something dramatic happened - like the watch fell to a concrete floor from 6 feet (or something like that) - Zenith should fix this for free. Inform them that a steel chronograph part like that should never break simply from normal use. I once had a problem with an El Primero (broken hammer spring) that was long out of warranty, and they took care of it with no issues at all. These are usually bullet-proof movements, if taken care of properly. Throw a little shame their way (assuming it's just from normal wear), and I suspect they will take care of it. I've owned several watches with the El Primero movement, and generally had no issues other than that one. Good luck!
