LX 283 then U2 6842 at Zurich
Johannesburg → Zurich → Porto
Timetable, Zurich time
06:10LX 283 from Johannesburg at the gate
21:40U2 6842 to Porto leaves the gate
15 h 30 apart on the timetable
U2 6842 leaves 15 h 30 after LX 283 arrives on the timetable: more than half a day, so not a connection we count.