Hi. If any one runs into error when trying to sendfirm to x fi in recovery mode under Windows 10, it is because of MTP driver issue. The solution is:
(1) Go to C:\Windows\INF
(2) Type "wpdmtp.inf" in search bar provided to the right of the address bar in Windows 10.
(3) Once you found it, just right click on it and select install. It will take a very few seconds.
(4) Connect your device to the pc.
After such procedure, the x fi will immediately be recognised. Then you can proceed with the steps listed out in the zen thread.