First of all you connect printer with USB cable and allow windows to install it. It will be ready for wired printing. Now you can go to Control panel and Add Device (not Add Printer but Add Device).
It will install device with printer icon but it is not a printer yet. Go to properties, hardware and note COM port number on which it is installed.
Only now you go to Control Panel, Add printer, Choose Local-not Bluetooth, create COM port with the same number you noted if it is not available yet and install drivers by choosing ZD420, add pairing code when requested and here your misery should end. You can read through thousands of forums about this issue online - maybe some solutions will help you, maybe not. I tried myself two dongles on two computers and failed to install properly but on laptop with build in Bluetooth it went like through butter. Please bear in mind that bluetooth is used not for printing labels but for printer configuration. For installation instructions on a Mac please watch this video on Youtube.
To print from iPhone or iPad you need Air Printer app installed and running on Bluetooth enabled computer to which printer is connected. Then you can print from Air Printer app installed on iPhone or iPad. Non of Zebra Label printers are AirPrint enabled.