<zk>
<vlayout width="100%">

<textbox hflex="1" value="hello"/>
<textbox mold="rounded" hflex="1" rows="2" value="I've got the mold rounded and I don't display my width properly"/>
<textbox hflex="1" rows="2" value="I've got the mold default and I display my width properly"/>

</vlayout>
</zk>

You can also try it like this, it doesn't work:
<textbox mold="rounded" width="100%" rows="2" value="I've got the mold rounded and I don't display my width properly"/>