If you complete the regular game (the .exe one) you will see how to do it.
In any case I'll write here how to read the password:
1. Get the GBA rom
2. Change the extension from .gba to .txt
3. Open it with a text editor and look for the word "password" (ctrl+f)
If you can't change the extension, try to use the "open with" option.
I'll just say, you'll need an emulator or a specific console to continue with the process lol, also, to open that zip use RAR since the file explorer from windows won't see that there is a password.
And yes, all this is intentional, my idea is to not only make a terrible game, this game isn't accesible in purpose. (Remember that the main game is the .exe one anyways)