Hey! I'm not an expert on this subject, but I might be able to get you a few steps closer to your goal.
First, if you don't already have it, download GCncrypt
. It'll help you convert AR code to RAW, and vice versa.
Make sure you read its documentation before using it.
Next, you'll need a workable copy of both the (US) and (JP) versions of the game.
I would recommend using Dolphin
to create RAM dumps of both versions
Here's a ROM of the US version: https://romhustler.net/rom/gamecube/resident-evil-zero-uThis tutorial
should help you understand where to proceed from there.