IIRC from Dave, it’s the same motor, same gear box, and custom wound for Duo (hence different). The zero perhaps consume a bit more power than the duo.
Re-load on the motor, I did raise this point / doubt elsewhere on this thread earlier and in my chat with Dave that sporting another burrs set might put more pressure on the motor (and gear box). It might therefore require different customisation, RPM, and prolonged testing for a given burrs set than designed and tested for mazzer. We won’t know unless alternate burrs are tested extensively.
Perhaps, are these the reason why the other grinders have significantly significantly higher motor power and faster RPM? But, some may still stall.