Complex sentence: Greenbaum was an official co-host of the 2010 Times Square New Year's Eve World Wide Webcast, which was watched live by over 500,000 viewers, and was the host of the New York Innovative Theatre Awards, held at Cooper Union's Great Hall.
Split into simpler sentences: Greenbaum was an official co-host for the 2010 Times Square New Year's Eve World Wide Webcast, which was watched live by over 500,000 viewers. He was also the host of the New York Innovative Theatre Awards, held at Cooper Union's Great Hall.