BA 725 then BA 580 at Heathrow
Zurich → London → Milan
Timetable, London time
07:45BA 725 from Zurich at the gate
07:10BA 580 to Milan leaves the gate
23 h 25 apart on the timetable, overnight
BA 580 leaves 23 h 25 after BA 725 arrives on the timetable: more than half a day, so not a connection we count.