If you’re in resistance mode these types of efforts are best done on climbs. Here’s a quick breakdown of the longer climbs on Zwift by rough duration:
Watopia
Epic KOM/Epic KOM Reverse - 16 - 20mins
Alpe D’Zwift - 45mins - 1hr
Volcano KOM - 6 - 8 min
Reverse KOM - 3.5 - 5 min
Forward KOM - 90s - 3 min
Innsbruck
Forward/Reverse KOM - 16 - 20 mins
London
Box/Fox Hill - 5.5 - 8mins
Keith/Leith Hill - 9 - 12 mins
NYC
Forward/Reverse KOM - 3.5 - 6 mins
(Bear in mind there’s a 3 - 5 min climb to get to the segment on NYC)
France
Petite KOM - 5 - 8mins
Ventoux - 60 - 120 mins