Emulate Zebra printer [duplicate]
Take a look at ZPLViewer - it works relatively well for rendering simple ZPL code but seems to fail on anything complex.
Best bet is just to purchase a printer. You can get a ZP-450 for $200. Get one with Ethernet ($100 more) and you can use the printer admin page to upload ZPL and render on-screen so you don't have to spew labels.
Here is a link to software that Zebra created: ZebraDesigner. It does not actually visualize ZPL or take ZPL as input. But it can help you design your ticket and then export it to ZPL for further processing.
I wrote https://github.com/dpavlin/Printer-Zebra a few days ago which converts ZPL ~DG (download graphics) commands and converts it back to PBM image file.
This is not full ZPL interpreter (since it only implements one command :-) but does work for cups generated ZPL files which is handy to find out if your printer output includes anti-aliased barcodes which are always bad...