http://theflamingskull.com/downloads/z00a/MM_BL_STUFF/M_BL_upgrade_for_zf2_551ml_6.0.zip
The ZIP contains the necessary files (Bootloader and TWRP), the scripts to automate the process and a README text. The error messages are normal and wont cause any trouble. For more info, check the CM13 or CM14.1 threads.
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Which Gapps are you using?