This is with reference to the two passages
Then all the people of Judah took Uzziah, who was sixteen years old, and made him king in the room of his father Amaziah.
2 He built Eloth, and restored it to Judah, after that the king slept with his fathers.
3 Sixteen years old was Uzziah when he began to reign, and he reigned fifty and two years in Jerusalem. His mother's name also was Jecoliah of Jerusalem.
and 2 Kings 15:
In the twenty and seventh year of Jeroboam king of Israel began Azariah son of Amaziah king of Judah to reign.
2 Sixteen years old was he when he began to reign, and he reigned two and fifty years in Jerusalem. And his mother's name was Jecholiah of Jerusalem.
It seems pretty clear that both the chapters are referring to the same person? Why then are the names mentioned different?