OK, so I saved zp-config.php with UTF-8 encoding.
I added polish letter to the gallery title and I can see it on titlebar now

For editing text files (php, html ...) I use notepad2
http://www.flos-freeware.ch/notepad2.html which has a lot of useful features,
like for example changing encoding from ANSI to UTF-8
ZP is Godsend