Using the zul below the problem can be seen. A listbox in a vbox resizes correctly if width/hflex set properly, but only gets bigger if placed inside a tablelayout. The tablechildren width/hflex doesn't seem to change anything. See the attached gif for a screencam of the issue.

<window title="Resize Issue Test Window" border="normal" width="200px" sizable="true">
<vbox width="100%" hflex="1">

<vbox width="100%" hflex="1">
<listbox width="100%" hflex="1">
<listhead>
<listheader label="Resizes"/>
<listheader label="Properly"/>
</listhead>
<listitem>
<listcell label="Test Cell"/>
<listcell label="Test Cell"/>
</listitem>
</listbox>
</vbox>

<tablelayout width="100%" hflex="1">
<tablechildren width="100%" hflex="1">
<listbox width="100%" hflex="1">
<listhead>
<listheader label="Grows but"/>
<listheader label="Doesn't shrink"/>
</listhead>
<listitem>
<listcell label="Test Cell"/>
<listcell label="Test Cell"/>
</listitem>
</listbox>
</tablechildren>
</tablelayout>

</vbox>
</window>