Hello,
I am finally finding time to work further on trying to add support for Japanese (some issues with zones, as well as adding language and hiragana fields) to OPC.
I have had to disable OPC because while it worked beautifully for guest checkout and registrations, it gave an error when trying to add addresses, since my shop's user creation and address book registration/changing code has been modified to support the needs of users here in Japan (selecting a language for the address, so that users can register an address in either English or Japanese, and then fields for hiragana name/surname as appropriate, plus multilanguage zone and country support).

I am working now using the code of OPC 2.3.4.

I suspect most of my work will be limited to editing files in includes/modules/pages/checkout_one/, with no changes needed in modules/pages/create_account/ unless I want to change the default population of an account.

I understand I will need to change the function "saveAddressValues" in the file jquery.checkout_one.js. This seems fairly simple.

However, in the file jquery.checkout_one_addr.js there is mention of an array "z2c" in function "updateCountryZone", but I cannot find this anywhere.
Apparently it is supposed to be supplied by jscript_main.php, but there is no mention of it there. I definitely need to edit the creation of this array. Can anyone point out where I may find it?