Are you using a pin or password screen lock? The latest twrp doesn't seem to be able to decrypt the ROM for updating. You need to change screen lock to pattern and it should work.
Just wondering why you are trying to flash by fastboot? Are you going back to stock Chinese?
If you are just doing an update or flashing different branch, just put it on your phone's internal memory or OTG usb stick and install the .zip file from twrp. Just remember to format data if it's a branch change or just a dalvik and cache wipe on an update.