Molds Bootstra
Abra o arquivo zk.xml

e adicione as seguintes library-property:
<library-property>
<name>org.zkoss.zul.Button.mold</name>
<value>bs</value>
</library-property>
<library-property>
<name>org.zkoss.zul.Menupopup.mold</name>
<value>bs</value>
</library-property>
<library-property>
<name>org.zkoss.zkmax.zul.Navbar.mold</name>
<value>bs</value>
</library-property>
<library-property>
<name>org.zkoss.zul.Paging.mold</name>
<value>bs</value>
</library-property>
<library-property>
<name>org.zkoss.zul.Panel.mold</name>
<value>bs</value>
</library-property>