Complex sentence: Tristram Shapeero, who directed several episodes during the first three seasons, was promoted to an executive producer and directed the majority of the season four episodes, while former showrunner Dan Harmon is credited as an "executive consultant".
Split into simpler sentences: Tristram Shapeero, whom directed several episodes during the first three seasons, was promoted to an executive producer and directed the majority of the season four episodes. While former showrunner Dan Harmon is credited as an "executive consultant".