UA 52 then LX 1850 at Zurich
Washington → Zurich → Thessaloniki
Timetable, Zurich time
07:40UA 52 from Washington at the gate
06:50LX 1850 to Thessaloniki leaves the gate
23 h 10 apart on the timetable, overnight
LX 1850 leaves 23 h 10 after UA 52 arrives on the timetable: more than half a day, so not a connection we count.