I don't use z wave so can't comment on the relative merits of either nor have I actually had to go through metal. If you had another device (zwave/zigbee) to test with it should give you a reasonable indication of whether the motion sensor would work reliably.
However from what I've though read z wave might be better than zigbee in this case but the best outcome would almost certainly be had if the hub can be positioned as close as possible to the sensor(s).
Another thing to consider might be adding an External Antenna . Not sure if @lewis.heidrick is still doing these mods. An antenna would certainly boost the receiving gain of your hub.
