Complex sentence: In May 2004, Mustaine returned to his newest recordings, intended as a solo effort, but, due to outstanding contractual obligations with the band's European label, EMI, he was forced to release it as a Megadeth album instead.
Split into simpler sentences: In May 2004, Mustaine returned to his newest recordings, intended as a solo effort. However, due to outstanding contractual obligations with the band's European label, EMI, he was forced to release it as a Megadeth album instead.