Complex sentence: In 1570 Trịnh Kiểm died and was succeeded by his second son Trịnh Tùng, a vigorous leader who captured Hanoi from the Mạc king in 1572.
Split into simpler sentences: In 1570 Trịnh Kiểm died and was succeeded by his second son Trịnh Tùng. Tùng was a very vigorous leader and he captured Hanoi from the Mạc king in 1572.