Complex sentence: All but two of the duo's studio albums are certified platinum or higher by the Recording Industry Association of America; their highest-certified is their 1991 debut "Brand New Man", which is certified sextuple-platinum for shipments of six million copies.
Split into simpler sentences: All but two of the duo's studio albums are certified platinum or higher by the Recording Industry Association of America. Their highest-certified is their 1991 debut "Brand New Man", which is certified sextuple-platinum for shipments of six million copies.