Complex sentence: MalcolmX also served as a mentor and confidant to Elijah Muhammad's son, Warith Deen Muhammad, who expressed to MalcolmX his skepticism of his father's "unorthodox approach" to Islam.
Split into simpler sentences: MalcolmX also served as a mentor to Elijah Muhammad's son, Warith Deen Muhammad. He was a confidant to Warith Deen, and the latter expressed to MalcolmX his skepticism of his father's "unorthodox approach" to Islam.