My wife rides more casually than me (hence doesn’t have a power meter). After getting her setup on my kurt kinetic trainer with zpower, it seemed like the power reading were really low.
If seems that one should be able to calibrate a power curve for zpower if one has a power meter. Do some ride say at 100, 200, 300 and 400w and then let zwift calculate the real world power curve for the trainer from the power meter.