hmm I should look up the details, but at first sight I would create use xpath to select all element9 elements...
Code:
<xsl:element name = "vraag">
<xsl:for-each select="element9">
<xsl:template-match />
<xsl:for-each/>
</xsl:element>
just out of my thumb, but I could be wrong, if I would be you I should check the documents at
www.w3.org