The problem is that the files generated by the "Write to file" action by ZP itself is not in UTF-8 (Write a blank line to generate file, then use Bind to file to add data). Loading a such generated file into a list will give me "different from UTF-8" error.
There's no cyrillic and chinese characters in those files, and I am using an English version of Windows, even though I have selected Chinese as the language for non-unicode programs in Control Panel.
Now ZP is not accepting the files ZP generates.