ZS for an motor run off an inverter

You could but it doesn't mean very much because it will never happen. The Zs to the inverter input terminals is the thing to test, that is as far as normal CPD operation can occur. If you short the output to Earth, or the motor becomes faulty, the electronics will limit the current to a safe level, and probably the CPD will be unaffected. Faults in the electronics could operate the CPD, but an Earth fault is unlikely and you have just measured that anyway. VSDs are really a kind of additional protection, which is fully electronic, and testing them is rather beyond normal MFTs. The Zs to the input is necessary to be OK for normal CPD operation. BTW they limit fault currents to protect themselves, and to some extent the Motor, but the motor does not have an overload or starter, as these functions pass to the VSD. All the settings are there in the manual, along with maximum speed, max current, minimum speed, start time, overload current, normal operating current, electronic braking, and usually a host of other stuff. There is nothing else to worry about!

You could but it doesn't mean very much because it will never happen. The Zs to the inverter input terminals is the thing to test, that is as far as normal CPD operation can occur. If you short the output to Earth, or the motor becomes faulty, the electronics will limit the current to a safe level, and probably the CPD will be unaffected. Faults in the electronics could operate the CPD, but an Earth fault is unlikely and you have just measured that anyway. VSDs are really a kind of additional protection, which is fully electronic, and testing them is rather beyond normal MFTs. The Zs to the input is necessary to be OK for normal CPD operation. BTW they limit fault currents to protect themselves, and to some extent the Motor, but the motor does not have an overload or starter, as these functions pass to the VSD. All the settings are there in the manual, along with maximum speed, max current, minimum speed, start time, overload current, normal operating current, electronic braking, and usually a host of other stuff. There is nothing else to worry about!