Zimri was king in Tirzah for all of seven days during the twenty-seventh year of the reign of Asa king of Judah. The Israelite army was on maneuvers near the Philistine town of Gibbethon at the time.
When they got the report, "Zimri has conspired against the king and killed him," right there in the camp they made Omri, commander of the army, king.
Omri and the army immediately left Gibbethon and attacked Tirzah.
When Zimri saw that he was surrounded and as good as dead, he entered the palace citadel, set the place on fire, and died.
It was a fit end for his sins, for living a flagrantly evil life before God, walking in the footsteps of Jeroboam, sinning and then dragging Israel into his sins.
As for the rest of Zimri's life, along with his infamous conspiracy, it's all written in The Chronicles of the Kings of Israel.