Zynga is mainly based on Facebook's platform. They also explicitly said that getting revenue on that platform is harder than expected. That makes investors very nervous about FB's outlook. We'll know more tomorrow when FB releases their own performance and expectation numbers.
FB is down 7% after hours, and the most likely culprit is this news, as the two companies' outlooks and stock performance have been tightly coupled after past quarterly reports.
I don't see where the FB also failing comes into the picture.