Complex sentence: He played guitar with them during 1990--1991 and performed on their "Devoured Carcass" EP before he began his solo musical project named Burzum, and quickly became involved with the early Norwegian black metal scene.
Split into simpler sentences: He played guitar with them during 1990--1991 and performed on their "Devoured Carcass" EP. In 1991, Vikernes began a solo musical project named Burzum, and quickly became involved with the early Norwegian black metal scene.