public class ContactEditVM {

    private String test;

    public String getTest() {
        return test;
    }

    public void setTest(String test) {
        this.test = test;
    }
}

<zk xmlns="http://www.zkoss.org/2005/zul">
    <window apply="org.zkoss.bind.BindComposer" viewModel="@id('vm') @init('avokado.addresses.ContactEditVM')" width="100%" vflex="min">
combobox model="@bind(vm.values)" selectedItem="@bind(vm.test)" width="100%" />
</window>
</zk>