<zk>
   <tree multiple="true" checkmark="true" height="300px" width="200px">
      <treecols>
         <treecol label = "tree"/>
      </treecols>
      <treechildren>
         <treeitem>
            <treerow>
               <treecell label="1"/>
            </treerow>
         </treeitem>
         <treeitem open="false">
            <treerow>
               <treecell label="2"/>
            </treerow>
            <treechildren>
               <treeitem>
                  <treerow>
                     <treecell label="2.1"/>
                  </treerow>
              </treeitem>
            </treechildren>
         </treeitem>
      </treechildren>
   </tree>
</zk>