Complex sentence: Although Donner had shot approximately 70% of the film, Lester jettisoned or reshot much of the original footage in order to be credited for the picture, resulting in his receiving sole credit for directing "Superman II".
Split into simpler sentences: Although Donner had shot 70%, give or take of the film, Lester jettisoned or reshot much of the original footage in order to be credited for the picture. Resulting in Lester receiving sole credit for directing "Superman II".