Complex sentence: The winners and runners-up of each of the eight groups in the group stage advanced to the round of 16, with both West Region (Groups A--D) and East Region (Groups E--H) having eight qualified teams.
Split into simpler sentences: The winners and runners-up of each of the eight groups in the group stage advance to the round of 16. Both West Region (Groups A--D) and East Region (Groups E--H) have eight qualified teams.