It gained full control of the project, previously known as Timok, after acquiring Nevsun Resources then Freeport-McMoRan's stake in Timok's Lower Zone in 2019.
The underground mine is expected to produce 50,000 tonnes of copper and 3t of gold in 2021, Zijin said, with the first part of the project targeting "an ultra-high grade orebody".
Zijin this month reported a net profit of CNY11.3 billion for the first nine months of this year, "the first time it has broken through the CNY10 billion mark".
"This equates to some US$1.76 billion, meaning it is rapidly positioning itself among the global Tier 1 miners," Zijin said.
The company has been boosted by "new world-class mining projects" being put into operation this year, including the start-up of its Kakula copper joint venture with Ivanhoe Mines in the Democratic Republic of Congo.
Serbia is expected to become Europe's second-largest copper producer, after Poland, as Cukaru Peki ramps up.
Zijin is also expanding operations at its Bor complex in the country's east, where it acquired a 63% stake in 2018.
Zijin had produced 52,000t of copper there in 2020 and said in June it expected to produce 120,000t of mined copper and 180,000t of copper cathodes every year once the expansion was complete.
The complex comprises four mines and a smelter, and Zijin said last month it had invested $142 million to improve local ecology and the environment.