The command ! U1 setvar "device.languages" "zpl" does not work. However ! U1 getvar "device.languages" does work but always returns "line_print" even after executing the setvar command.
Printer's model is MZ 320. Any help is much appreciated. Thanks!
MZ320 does not support ZPL, it only supports CPCL. The MZ320 was discontinued earlier this year (see the product page: MZ320 Mobile Printer Support & Downloads | Zebra ). The successor product, iMZ320, DOES have ZPL support.
Hope that helps.