PFsense : Reclaiming disk space from thin provisioned VMDK files on ESXi 7

[maba]

Hello,
I have a problem with the thin-disk vmfs5 of the pfsense virtual machine. I have allocated 50 go , it barely use 2go with zfs ...
The problem is , vmfs5 don't automaticly reclaim unused space ... so the vmdk grow to 50Go .... and i am running out of space for esxi ;)
So i want to reclaim this space , but i am not sure if i am going to do it right (i don't know exactly how pfsense mount is volume ...) , vmware blog write you must "zeroing" all unused space in the vm and then use vmkfstools.

So, after have shutdown as many services as i can, if i ssh to pfsense, choose shell, cd / and enter:
dd if=/dev/zero of=/zeroes && rm -f /zeroes

this should do the trick ? I am not confortable with this command because it reach the "out of space" of the disk.
what is correct procedure to do this ? (i have barely space to recreate a 10Gb disk and reimport pfsense setting from scratch).

Thanks for your help ;)