While we can't provide technical support on printer settings, you can find guides below that may help you set up your printer. If you encounter any issues, you will need to liaise with your printer manufacturer.
Guides for Zebra ZD421D
Printer installation guide for Windows
Printer installation guide for Mac OS
Printer installation guide for Chromebooks
Printer installation guide for Android Devices
Guides for Zebra GK420D (discontinued)
Printer installation guide for Mac OSX 10.10
Printer installation guide for Zebra LP2844/GK420D - updated June 2017