Complex sentence: Zack brought in Marchais and Pretorius and was forced to take on a fourth man, Corsican Dominique Orsini: it was Orsini who gave Simon the belt that killed him.
Split into simpler sentences: Zack brought in Marchais and Pretorius and was forced to take on a fourth man, Corsican Dominique Orsini. It was Orsini who gave Simon the belt that killed him.