Hi,
it's not(or not so easy) possible. Linux power down is only for the ZynqMP.
if you want to power off all, you must check if you can send some power down signal from zynq to CPLD (Maybe over MIO or PL IO --> some are connected to CPLD) and change CPLD firmware to power down all (CPLD source code is available on the download area)
br
John