The z-racks have two frame attachment points. Your Brick's frame has been cut back so has eliminated the rearmost frame mount. The forward frame mount was located near the rear end of the sheetmetal frame gusset to which the seat post lock mounted on the shifter side of the Brick. Your side-profile photo isn't detailed enough to determine whether that mount is still there. Furthermore, the lower mount on the z-racks attached to two holes on the foot peg plates and it seems they have been removed.
As currently configured, your Brick's frame is unlikely to provide sufficient stability for z-racks and cases.
