I keep meeting Odoo customers who need to print zebra labels but don't want to maintain a label-template editor. Built zpl-creator — drag-drop a barcode/sku/text, get raw ZPL out the other end. Wired into the inventory module so warehouse staff hit one button on a picking and the printer spits the right label.
What I learned: ZPL is incredibly forgiving. Spec docs read like a 1985 service manual but the printer just executes whatever text you throw at it. The interesting work is in the live preview — turning ZPL back into pixels in the browser so people can WYSIWYG their labels.
Open-source, GPLv3. Pull requests welcome.