SG 621 then 6E 5156 at Mumbai
Udaipur → Mumbai → Dehradun
Timetable, Mumbai time
20:45SG 621 from Udaipur at the gate
15:406E 5156 to Dehradun leaves the gate
18 h 55 apart on the timetable, overnight
6E 5156 leaves 18 h 55 after SG 621 arrives on the timetable: more than half a day, so not a connection we count.