EC 3749 then IB 5374 at Barcelona
Milan → Barcelona → Firenze
Timetable, Barcelona time
21:30EC 3749 from Milan at the gate
15:40IB 5374 to Firenze leaves the gatealso LL 5374, VY 6074
18 h 10 apart on the timetable, overnight
IB 5374 leaves 18 h 10 after EC 3749 arrives on the timetable: more than half a day, so not a connection we count.