Conversation so far:
what happened in 2001 for The Smashing Pumpkins?
In 2001 the compilation Rotten Apples was released.
what did Billy Corgan of The Smashing Pumpkins do in chicago?
Billy Corgan and Jimmy Chamberlin reunited in 2001 as members of Corgan's next project, the short-lived supergroup Zwan.
what songs did Billy Corgan and Jimmy Chamberlin write as members the supergroup Zwan?
The group's only album, Mary Star of the Sea, was released in 2003.

Question: what was their biggest accomplishment?
Self-contained rewrite: what was the band Zwan's biggest accomplishment?