the ItsNat Author's challenge

<vbox id="vbox">
<zscript><![CDATA[
    String[] arr = {"Click Me!", "Cannot be Clicked"};
]]></zscript>
    <label id="lb1" value="${arr[0]}"/>
    <label id="lb2" value="${arr[1]}"/>
    
<zscript><![CDATA[//@DECLARATION
    org.zkoss.zk.ui.event.EventListener evtListener = new org.zkoss.zk.ui.event.EventListener(){
        public void onEvent(Event evt){
                evt.getTarget().removeEventListener("onClick", evtListener);
                evt.getTarget().setValue(arr[1]);
                if(evt.getTarget().equals(lb1)){
                    lb2.addEventListener("onClick", evtListener);
                    lb2.setValue(arr[0]);
                }else{
                    lb1.addEventListener("onClick", evtListener);
                    lb1.setValue(arr[0]);
                }
                new Label(evt.getTarget().getId()+" clicked").setParent(vbox);
        }};
]]><![CDATA[
    lb1.addEventListener("onClick", evtListener);
]]></zscript>
</vbox>