Ok, if the browser sends POST/PUT request with a JSON structure it also sends charset = utf8 (in my case). That's ok, because for JSON this is more or less the default charset.
Zinc now seems to notice, that UTF8 charset is needed and creates a ZnStringEntity with an UTF8Encoder. Now when my application tries to get the JSON string of that ZnStringEntity and builds the structure out of that string - and the strings are NOT UTF8, but converted to (?) ISO8859 ? Marten -- Marten Feldtmann