Is it possible to install a ROM from TWRP ADB shell? Let's say I place a rom in /sdcard/. Can I install in the ADB shell through TWRP. For instance, if I 


Start up in recovery of TWRP
Type in on the host adb shell


Is there anyway to install /sdcard/rom.zip
The TWRP provides a command line utility called twrp and the official site has a guide to twrp's subcommands of which the command needed is simply install

install FILENAME :

    install FILENAME zip file.


Usage: under adb shell environment, run
twrp install /path/to/rom.zip