I forgot the lock screen PIN on my Moto G second gen XT-1068
Did you set up and activate either Google's Android Device Manager or Motorola Device Policy (Settings/Security/Device Administrators)? Both allow you to set a new password remotely (which would clear the forgotten PIN), via either https://www.google.com/android/devicemanager or the Moto Support Site respectively.

If so it might be worth giving it a try although if you did manage to Factory Reset the phone that should have removed your Google account. I'm surprised that the PIN survived a Factory Reset.