The source code of a working demo of printing labels over Bluetooth Low Energy on iOS is available on Zebra GitHub.
Zebra printers of ZQ300 & ZQ500 series mobile printers, ZD400 & ZD600 series desktop printers, and ZT600 series industrial printers have both Bluetooth Classic and Low Energy (LE) capabilities. We have created a demo project in Xcode to show how to scan, connect, send ZPL to and read data from a Bluetooth LE enabled Zebra printer on an iOS device. The Bluetooth LE on Zebra printer acts as a peripheral. A Bluetooth LE central device needs to connect to the printer first before it can start to discover the services and then to discover the characteristics. The source code of the demo is available for download on GitHub and called ZeBraPrinterBLEDemo. You can download this Xcode project, compile and run it on an iPhone straight away. For more details, please refer to the README.md of this demo on GitHub. Hope this provides a hands-on experience on how Bluetooth LE works with Zebra printers. Happy coding!