Replace light switch with z wave smart switch
The new smart switch requires a neutral so unless you have a couple white wires wire-nutted together in the box with the switch, you're out of luck using that switch. You'll need to get a switch that doesn't require a neutral.
If you have only two true black wires in the switch box, chances are you have conduit and you could pull some THHN from the ceiling to the switch and bring in a neutral but we'd need more pictures to verify that.