The backup folder will be created when the admin initialize the backup on the server, the default location is "/opt/zimbra/backup/zextras"

Removing the backup folder is not recommended which will break the backup.

here is the Zextras backup guide, hope you will find it interesting.

https://docs.zextras.com/suite/html/backup.html

if you still wish to remove the backup folder then you could stop and disable the module using CLI commands by running, then remove the folder,

make sure that you do not have any important data in that folder.

zxsuite backup setProperty ZxBackup_ModuleEnabledAtStartup false
zxsuite backup doStopService module

Thanks