Zheng was overseer of the construction of the planet's propulsion system during Mondas' darkest times (pre-conversion) and was also one of the few Cybermen whose body did not reject the processing.
Due to rioting caused by the Fifth Doctor, Zheng was summoned from the surface by the Central Committee to subdue the insurrection. After doing so, Zheng visited the main processing plant to quell interference from new recruits which had not received their full programming due to a power cut (caused by travelling through the Cherrybowl Nebula), killing one in doing so. After noticing that Sisterman Constant's scapula was fractured, he ordered her to be taken for processing which she would survive despite the high mortality rate.
Zheng then visited the Central Palace to make certain that Doctorman Allan's repairs to the generators were progressing. Despite the power loss, the Central Committee was still alive (albeit just barely) and requested Zheng's report, which he gave as:
- "Storm radiation intensity has increased two hundred and thirty percent. Endurance levels have been met. Final tests on the propulsion system were curtailed by the power loss."
As Doctorman Allan was unable to repair the generator due to its complex nature, the Doctor did it instead. Recalling the Doctor's name from the previous insurgencies, Zheng waited until his repairs were complete but reactivated the power early, seemingly eliminating him. However, the Doctor's Time Lord physiology prevented his death and Zheng allowed him to live at Doctorman Allan's urging; intending to use his smaller tertiary lobe as a template in all future cybermen, the first of these being a newly converted Thomas Dodd.
The Committee initialised city-wide processing, choosing this over operation of the propulsion system in order to escape the Nebula. Zheng, realising that the city would not survive much longer in the nebula, attempted to activate the propulsion system but was attacked by the Committee (now functioning below usual standards due to the Doctor sabotaging its nutrients with wine). Mortally wounded, Zheng ordered his surface crew to activate the propulsion system and clear the nebula. The Committee was destroyed by a large swarm of Cybermats which were attracted to its energy, allowing Doctorman Allan to supervise Mondas' future. However, the then-converted Cyberman Sisterman Constant suggested increased processing as a means of survival, which Allan laughed off until a reassembled Zheng stepped through the door. (AUDIO: Spare Parts)