Zebra Printer Label Sizes
The label size used by DMO when printing to a zebra printer is 97mm x 156mm Portrait.
Change this in the Layouts Tab>Settings>ZDesigner GK420D>Properties
When changing it from Packing Partner, sometimes this label size is not saved
If this happens set it as the default from Control Panel>Devices and Printers
You will need to close and open Packing Partner, for it to read the default properties