I'm using ZebraDesigner 2.2.2 (Build 2728).
Is there a way to extract the ZPL code from ZebraDesigner? I can't even export it to ZPL file, the only option I have is saving it as .lbl.

You can add a new ZebraDesigner ZPL driver to the system and use a file as the port. Then when you "Print" the document, it will write the ZPL code to the file.
Note that it might have some header information before the first ^XA which you might not need.
UPDATE : (How to add local port on a driver)
Printer PropertiesPorts tabAdd PortLocal Port and click New portC:\output.zplC:\output.zpl