Nanyang, Henan
Zheng was from Nanyang Commandery (roughly modern Nanyang, Henan) -- the same commandery that the Eastern Han imperial clan dominated. He was described to be cautious, agile, and a deep thinker. He first served in the household of Emperor Zhang while he was still the crown prince under his father Emperor Ming. After Emperor Zhang ascended the throne, he was eventually promoted to the post of an imperial attendant (中常侍).