This treason refers to Zimri's plot to kill Elah, the king of Israel. The full meaning of this statement can be made clear. Alternate translation: "how he plotted against King Elah" or "how he killed the king of Israel" (See: [[rc://en/ta/man/translate/figs-explicit]])
This question is used to either inform or remind the readers that the information about Zimri is in this other book. This rhetorical question can be translated as a statement. See how you translated a similar phrase concerning Judah in [1 Kings 14:29](../14/29.md). Alternate translation: "they are written in the book of the events of the kings of Israel." (See: [[rc://en/ta/man/translate/figs-rquestion]])
This can be stated in active form. Alternate translation: "someone has written about them in the book of the events of the kings of Israel." (See: [[rc://en/ta/man/translate/figs-activepassive]])