Zoo, son of Tahmasp, was a righteous Pishdadian king descended from Fereydun. Selected at the age of eighty by Zal and the Iranian nobility following King Nowzar's death and Afrasiab's invasion, Zoo brought wisdom and Kayanid strength to the throne. During his reign, a severe eight-month drought halted war between Iran and Turan, leading both nations to sign a historic peace treaty dividing the world. After peace was established, rain returned, and Zoo ruled justly for five years until his death.