CZ 3391 then ZH 121 at Guangzhou
Zhengzhou → Guangzhou → Hanoi
Timetable, Guangzhou time
12:30CZ 3391 from Zhengzhou at the gate
11:25ZH 121 to Hanoi leaves the gate
22 h 55 apart on the timetable, overnight
ZH 121 leaves 22 h 55 after CZ 3391 arrives on the timetable: more than half a day, so not a connection we count.