There are two kings named Jehoram and two kings named Ahaziah in 2 Kings. In both cases the kings with the same name are kings at the same time - one of Judah and one of Israel. To make things even more confusing, Jehoram is often called Joram. In this chapter, Joram is king Jehoram of Israel and Ahaziah is the king of Judah. I'll do my best to keep them straight for you.
Throw his [Joram's] body in the field of Naboth, according to the word of the Lord. (9:24)
Now that promise is being fulfilled by having Ahab's son, Joram, killed and and his body thrown into the field of Naboth - which is the field that Ahab and Jezebel got by having Naboth falsely accused of blasphemy (1 Kings 21:7-15. Episode 144)
Is it peace, Zimri, murderer of your master? (9:31)