ZKOSS - creating new css theme

[aelvirra]

I am new to Zkoss and i need to create completely new css theme for my pages. In documentation I found that it can be done by overwriting default z-classes. So I created my own classes like \[code\].z-datebox-inp\[/code\] etc. (according to styleguide) but when I inspect elements on page, they have rules from both classes, Zkoss default(comes from zk.wcs) and my custom class (my css file). Sometimes zkoss default class even overrides mine so I have to add \[code\]body\[/code\] selector before my class name to make it prior to browser. Is there any way to get rid of zkoss default css styles completely or do I have to rewrite every single css rule that comes from default class? Any help would be appreciated. Thanks.