Pretty sure you can just rename the ota to otz, I compared the ota with a Zooz otz and they look to be the same format. I am testing on my DZPD3 right now, still uploading.
EDIT: It worked and I got back status code 255
255:"New image was successfully stored in temporary non-volatile memory. The device will now start storing the new image in primary non-volatile memory dedicated to executable code. Then the device will restart itself."
This is the device kicking this error back, so its not really an HE issue I dont think.
You could try renaming the ota file to otz and using the built in updater app.
I was able to send the update to a DZPD3 using that method just now. Mine was already updated but it took it and flashed it, did not fail.
