I just came across this post where Leviton firmware v1.22 was posted just 17 days ago so I’m duplicating the information here. The models with updates are:
- DZ6HD DZ6HD_v1_22.ota.zip
- DZ15S DZ15S_v1_22.ota.zip
- DZPA1 DZPA1_v1_22.ota.zip
- DZPD3 DZPD3_v1_22.ota.zip
Notes:
- These are OTA updates and can be used directly in zwavejs2mqtt
- It can take a very long time for the update to happen so watch the device list which looks like this when in progress:
This update has been running for at least 20 minutes at this point and is less than halfway.
That update took well over an hour. I moved a 2nd device next to the controller and it took ONLY an hour. 
EDIT: You may have to restart the update, perhaps several times, before it succeeds.