Complex sentence: Charles Dillingham hired Golden, already well-known as a lyricist and producer, to work on his "Hip-Hip-Hooray", which opened at the Hippodrome on 30 September 1915 and ran for 425 performances.
Split into simpler sentences: Charles Dillingham hired Golden, now well-known as a lyricist, to work on his "Hip-Hip-Hooray". It opened at the Hippodrome on 30 September 1915 and ran for 425 performances.