For this i would use 7zip although winrar also should work.
If i remember right, the only thing you need to change is in global.ini
For example my global.ini settings for language:
LanguageType = "de"
Datalanguage = "eneu"
Stringlanguage = "eneu"
this is my country.ini from update.inf
[BOOT]list=eneu:Europe
[United States]defaultselect=enus
[Canada]defaultselect=enus
[United Kingdom]defaultselect=eneu
[Australia]defaultselect=eneu
[Germany]defaultselect=eneu
[Switzerland]defaultselect=eneu
[Austria]defaultselect=eneu
[Turkey]defaultselect=eneu
and localization from update.inf
[de]
country=de
language=de
datalanguage=de
langselect=de
eutsch,eneu:English
windowname=Runes of Magic
IsAutoHashPassword=1
specialEventFilter=halloween
Runedev.ini
[Locale]
Language=de
All German here