Complex sentence: In 2004, Choi won the grand prize in David Bowie's "Mashup" contest and appeared in "USA Weekend Magazine", alongside Usher, after he received the grand prize for the magazine's John Lennon Songwriting Contest for teens.
Split into simpler sentences: In 2004, Choi won the grand prize in David Bowie's "Mashup" contest. Appearing in "USA Weekend Magazine" with Usher, he received the grand prize for the magazine's John Lennon Songwriting Contest for teens.