Currently, the fastest train between Pune and Hubli is Karnataka Sampark Kranti Express, which covers the distance in 10 hours and 40 minutes. So assuming same speed/stops, the Duronto will reach UBL around 20.40.
The fastest return is 11:05 hours, which means the Duronto would have to leave UBL at 04.10 am.
That...
more... would give a layover of only about 7:30, which may be sufficient for LHB maintenance (if they have it at UBL), but any delay would result in delayed departures.