Move Up / Move Down buttons in Zerberus synth window to change the order of the loaded sfzs.
Packages load all soundfonts they have into the synth right after installation. If user had some sfzs loaded before, it will be a mess in the used pitches mapping, cause Zerberus uses the topmost available sfz in theis list with the required pitch.
You need delete sfzs and add them again if you want to reorder items.
The new up/down buttons are suggested to be added and used to change position of the selected sfz.