ZE550KL Flashing via Fastboot

fastboot-log.txt

C:\ft>fastboot.exe flash boot 16stock\16boot.img
target reported max download size of 268435456 bytes
sending 'boot' (24547 KB)...
OKAY [  0.774s]
writing 'boot'...
FAILED (remote: can't flash unsigned image)
finished. total time: 0.962s

C:\ft>fastboot.exe flash recovery 16stock\16recovery.img
target reported max download size of 268435456 bytes
sending 'recovery' (26505 KB)...
OKAY [  0.839s]
writing 'recovery'...
FAILED (remote: can't flash unsigned image)
finished. total time: 1.038s

C:\ft>fastboot.exe flash system 16stock\16system.img
target reported max download size of 268435456 bytes
erasing 'system'...
OKAY [  0.024s]
sending sparse 'system' (262143 KB)...
OKAY [  8.801s]
writing 'system'...
OKAY [ 10.704s]
sending sparse 'system' (250170 KB)...
OKAY [  8.438s]
writing 'system'...
OKAY [  4.306s]
sending sparse 'system' (262143 KB)...
OKAY [  8.798s]
writing 'system'...
OKAY [  4.194s]
sending sparse 'system' (235006 KB)...
OKAY [  7.890s]
writing 'system'...
OKAY [  3.870s]
sending sparse 'system' (260578 KB)...
OKAY [  8.731s]
writing 'system'...
OKAY [  4.107s]
sending sparse 'system' (251006 KB)...
OKAY [  8.444s]
writing 'system'...
OKAY [  3.894s]
sending sparse 'system' (245430 KB)...
OKAY [  8.372s]
writing 'system'...
OKAY [  3.884s]
sending sparse 'system' (260732 KB)...
OKAY [  8.686s]
writing 'system'...
OKAY [  3.855s]
sending sparse 'system' (229940 KB)...
OKAY [  7.718s]
writing 'system'...
OKAY [  3.684s]
sending sparse 'system' (256547 KB)...
OKAY [  8.582s]
writing 'system'...
OKAY [  4.158s]
sending sparse 'system' (257661 KB)...
OKAY [  8.661s]
writing 'system'...
OKAY [  3.892s]
sending sparse 'system' (171185 KB)...
OKAY [  5.759s]
writing 'system'...
OKAY [ 13.581s]
finished. total time: 163.146s

C:\ft>fastboot.exe oem reboot-recovery
...
OKAY [  0.002s]
finished. total time: 0.003s