As far as Zen Cart core code goes, those log files are generated by the PHP files you mentioned in your first post above.

So, either you didn't actually remove those files, or you've added something else which generates them, or you've configured something else into your webserver to generate them. Sorry, I can't help you beyond what the ZC core code files contain.

But really, fixing the root problem is always the best approach ... and it appears you're using an invalid character set, so switching it to a valid one would remove or change the error message.