The bridge was originally meant to be opened in October 2016, but has been beset by delays following legal challenges and a number of injuries and even deaths to workers.
His death comes only days before reportedly President Xi Jinping was due to visit Zhuhai next door to Macau, in order to open the Hong Kong-Zhuhai-Macau Bridge on Tuesday. Most drivers will have to park at the Hong Kong port, switching to shuttle bus or special hire cars once they are through immigration.
The 55-kilometre (34-mile) crossing, which includes a snaking road bridge and underwater tunnel, links Hong Kong's Lantau island to Zhuhai and the gambling enclave of Macau, across the waters of the Pearl River Estuary.
But officials say the bridge will cut journey times between the cities from three hours to just 30 minutes and will be in use for 120 years.
Zheng was director of China's Hong Kong and Macau Affairs Office, and was a member of the Chinese Communist Party's (CCP) top-level Central Committee.
According to Guo, Zheng and Meng knew each other well, and their misfortune is interlinked.
"Hong Kong has had to fund a lot of the bridge, but we won't see many benefits here", Mo said.
The Hong Kong-Zhuhai-Macao Bridge was built to withstand magnitude 8 earthquakes, a super typhoon and strikes by super-sized cargo vessels.
While an impressive engineering feat, the building of the bridge brought its own controversies.
Guo finished by speculating that Chinese officials from its public security services and the Central Commission for Discipline Inspection could also face danger in the future.