UA 784 then DL 3876 at Denver
Mexico City → Denver → Austin
Timetable, Denver time
11:54UA 784 from Mexico City at the gate
09:42DL 3876 to Austin leaves the gate
21 h 48 apart on the timetable, overnight
DL 3876 leaves 21 h 48 after UA 784 arrives on the timetable: more than half a day, so not a connection we count.