Complex sentence: Marley Marl spent the early nineties an in-demand producer, working most notably with LL Cool J in 1990 on "Mama Said Knock You Out", but it would also be the last year he would contribute to a Juice Crew member's album.
Split into simpler sentences: Marley Marl spent the early nineties as a producer, including work with LL Cool J in 1990 on "Mama Said Knock You Out". It would be the last year he would contribute to a Juice Crew member's album.