Complex sentence: Although the New Zealand Broadcasting Corporation never broadcast "The Crusade", due to a prohibitive rating from the censor board, NZBC never returned the films to the BBC or actively destroyed them.
Split into simpler sentences: Although the New Zealand Broadcasting Corporation received copies of "The Crusade", it never broadcast the serial due to a prohibitive rating from the censor board. After rejecting the serial, NZBC never returned its film prints to the BBC or actively destroyed them.