ZH 8904 then ZH 121 at Guangzhou
Zhengzhou → Guangzhou → Hanoi
Timetable, Guangzhou time
13:55ZH 8904 from Zhengzhou at the gate
11:25ZH 121 to Hanoi leaves the gate
21 h 30 apart on the timetable, overnight
ZH 121 leaves 21 h 30 after ZH 8904 arrives on the timetable: more than half a day, so not a connection we count.