According to op:

Hey everyone,
I managed to find an older version of KOF Zillion on a Chinese website called "m.962.net". I believe this might actually be the very first public version ever released.

• I stumbled upon it via Google Images while searching for "KOF Zillion 2006". Since the website is entirely in Chinese and quite sketchy to navigate, I want to give a huge shoutout to my friend Meldo. Using downloader2, he managed to safely grab the files for me.
  
• The original files were missing some executables required to run the game. It seems the creators encrypted it back then to prevent people from stealing the assets. Luckily, I managed to successfully decrypt the build using De-MOLE-ition, so it is now fully playable!
  
• I also need your help!!!

This build is from 2006, but I know that another version was released that same year. That other version had a completely different lifebar and a much more complete character roster. I am still actively looking for it. You can see screenshots of this and some video footage in my previous post: https://mugenfreeforall.com/topic/53680-does-anyone-own-this-rare-version-of-kof-zillion/

If anyone has that specific build or knows where to find it, please let me know!