This article is a work in progress.
At the moment, the firmware of the Zima isn't in the main QMK branch yet.
You can find the temporary firmware on the keyboard-zima branch on splitkb's Github. For an easy workaround, copy the
/keyboards/zima folder into your own
/keyboards folder, after which you can flash the macropad like you usually would (see Kyria Build Guide: Kyria Firmware for more detailed steps on how to flash).