So, I'm using UTAU PC on Mac via Parallels desktop, as stated in the title. I've tried unzipping the file on mac using the unarchiver, but the text in the app still appears as a jumble of letters and symbols when I open it in Windows.
Parallels functions as a virtual machine. You need to change the locale of the Windows OS inside the virtual machine before you can do anything with UTAU. https://www.java.com/en/download/help/locale.html