Who is Zhu Zhanji from When China Ruled the Seas: The Treasure Fleet of the Dragon Throne, 1405-1433 and what is their importance?

After his father, Zhu Gaozhi, died, Zhu Zhanji became Emperor of the Ming Dynasty. He reportedly had good qualities of both his grandfather, Zhu Di, and great-grandfather, Zhu Yuanzhang.