We'll update as we get more details (I'm at work and Kurt is busy being the UP version of Bob Vila), but according to the front office twitter:
Zumaya has a non-displaced fracture of olecranon (tip of elbow) and he will be sidelined for the remainder of the season.
What does this mean? Here's a quick link to the American Academy of Orthopaedic Surgeons. Ouch. According to the AAOS surgery is sometimes necessary to fix it, if the fracture is displaced. Since they say Joel's fracture is non-displaced, maybe he has escaped going under the knife yet again. There has been no speculation or comment as to whether he will be able to pitch in the future, though.
EDIT (3:59): Beck has an article up right now- he notes that the non-displaced fracture means that Zumaya's recovery time will be lower. -David