Conversation so far:
did Billy Corgan release any songs as a solo artist?
in 2004, he began a solo music career.
What is Zwan?
the band.
who else was in Zwan?
Corgan's old friend Matt Sweeney.
is anyone else in Zwan?
guitarist David Pajo and bassist Paz Lenchantin.
what type of music did Zwan play?
The band had two distinct incarnations, the primary approach being an upbeat rock band with a three-guitar-driven sound.
when did Zwan form?
2001.
Did they eventually break up?
formally announcing a breakup.

Question: why did they break up?
Self-contained rewrite: why did Zwan break up?