I am unfamiliar with the ZyXEL VMG8324-B10A so I shall use my VMG1312-B10D as an example.
Establish either an ssh or telnet connection to the device and from the Busybox shell interrogate the device for the vectoring status --
[Duo2 ~]$ ssh admin@ap
admin@ap's password:
BusyBox v1.20.1 (2016-10-18 15:41:48 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.
$ xdslctl info --vectoring
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 8000
Last initialization procedure status: 0
Max: Upstream rate = 996 Kbps, Downstream rate = 5636 Kbps
Bearer: 0, Upstream rate = 995 Kbps, Downstream rate = 5115 Kbps
Currently not in VDSL modulation --vectoring is only for VDSL mode
$ Connection to ap closed.
[Duo2 ~]$
You will need to check for the correct command usage, either xdslcmd or xdslctl would be my first two guesses.
Try either xdslcmd --help or xdslctl --help and see what result you obtain.