L=[ (A异或B) 异或 (C异或D) ]

=[ (A'B+AB') 异或 (C'D+CD') ]

=[ (A'B+AB')'(C'D+CD')+(A'B+AB')(C'D+CD')' ]

=[ (A同或B)(C异或D)+(A异或B)(C同或D) ]。