Are you using the old Jasco z-wave switch with no neutral? If that’s the case then it will work but only with incandescent bulb.
If you are using the newer GE smart switch that requires neutral then I would not recommend using it with no true neutral. Your switch will not last.
It would be best to go if it’s easy to run a neutral wire from your light fixture down to your switch box as stated by @jgravert . This way you will have more switch options. Unfortunately it’s Usually not as easy depend on your switch box and light fixture location.
You can follow this post here if you want to go with the micro relay module. You will be able to use the old switches to control the relay module on/off. Just not for dimming.