I came across an interesting thread in the Z-Wave JS repo that contains pointers to newer ota firmware updates for the DZ6HD and DZ15S, and I thought it worth posting info here. Leviton doesn't provide release notes so what all the changes are is unknown, but they are being recommended for performance/stability improvements.
Note that the Hubitat Device Firmware Updater app is not currently able to perform firmware updates for these Leviton devices. You will need to use a Z-Wave stick and PC Controller to perform the ota upgrade. If you don't have experience with PC Controller, I recommend waiting until Device Firmware Updater is updated to work with these devices.
I've updated over a hundred devices so far, the the firmware works well.
One additional item, if you are using the "Leviton DZ6HD Z-Wave Dimmer" driver, I recommend switching to the "Generic Z-Wave Smart Dimmer" driver. The DZ6HD specific driver appears to have a bug in which it queries the device for updates twice rather than just once. For the DZ15S, I use the "Generic Z-Wave Smart Switch" driver.