UA 3913 then AM 419 at Houston
Denver → Houston → Mexico City
Timetable, Houston time
21:22UA 3913 from Denver at the gate
11:19AM 419 to Mexico City leaves the gate
13 h 57 apart on the timetable, overnight
AM 419 leaves 13 h 57 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.