It's not an OTA-Update, you have to flash all files from the Firmware.zip. Take a look into the flashfile.xml in the ZIP, inside are all Flash commands for fastboot.
For example the RETEU 6.0.1 Version look like this:
For example the RETEU 6.0.1 Version look like this:
Code:
fastboot flash partition gpt.bin
fastboot flash bootloader bootloader.img
fastboot flash modem NON-HLOS.bin
fastboot flash fsg fsg.mbn
fastboot erase modemst1
fastboot erase modemst2
fastboot flash bluetooth BTFM.bin
fastboot flash dsp adspso.bin
fastboot flash logo logo.bin
fastboot flash boot boot.img
fastboot flash recovery recovery.img
fastboot flash system system.img_sparsechunk.0
fastboot flash system system.img_sparsechunk.1
fastboot flash system system.img_sparsechunk.2
fastboot flash system system.img_sparsechunk.3
fastboot flash system system.img_sparsechunk.4
fastboot flash system system.img_sparsechunk.5
fastboot flash system system.img_sparsechunk.6
fastboot flash system system.img_sparsechunk.7
fastboot flash system system.img_sparsechunk.8
fastboot flash system system.img_sparsechunk.9
fastboot flash system system.img_sparsechunk.10
fastboot flash system system.img_sparsechunk.11
fastboot flash system system.img_sparsechunk.12
fastboot flash system system.img_sparsechunk.13
fastboot flash oem oem.img
fastboot erase cache
fastboot erase userdata
fastboot erase customize
fastboot erase clogo
fastboot erase ddr
fastboot reboot