I will fly from Hongkong to Incheon airport, Korea via ZHENGZHOU (with Southern Airline)

First, I will fly from Incheon airport to Hongkong via Beijing.
And stay in Beijing less than 72hours and I know No visa required.

And layover in ZZ 2h10min and fly back to Korea.
Do I need to get China visa or don't need it? T-T