Complex sentence: Scaramucci's tenure of six days, from his unofficial start date on July 25 through his departure on July 31, is the shortest in history for that position, breaking the record of 11 days set by Jack Koehler in the Reagan administration.
Split into simpler sentences: Scaramucci's tenure of six days, from his unofficial start date on July 25 through his departure on July 31, is the shortest in history for that position. It broke the previous record of 11 days set by Jack Koehler in the Reagan administration.