Complex sentence: Compared with its N52 predecessor which was port-injected, the N53 uses direct injection (consisting of piezoelectric injectors directly in the cylinder) with a "stratified lean mixture" operation.
Split into simpler sentences: Compared with its N52 predecessor which was port-injected, the N53 uses direct injection. The direct injection system uses piezoelectric fuel injectors which inject into the combustion chamber, using a "stratified lean mixture" operation.