Complex sentence: Maryland was a member of the Atlantic Coast Conference (ACC) which along with the other two major athletic conferences in the South, the Southeastern Conference and the Southwestern Conference (now the Big 12), had no blacks playing football for any of their teams.
Split into simpler sentences: Maryland was a member of the Atlantic Coast Conference (ACC). Neither it nor the other two major athletic conferences in the South, the Southeastern Conference and the Southwestern Conference (now the Big 12), had any blacks playing football for any of their teams.