This is a complete conversion :
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="node()|@*">
<xsl:copy>
<xsl:apply-templates select="node()|@*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="body"/>
<xsl:template match="body[1]">
<body>
<xsl:apply-templates select="../body/node()"/>
</body>
</xsl:template>
</xsl:stylesheet>
when applied to the provided XML document:
<Content>
<body>
<text>xxx</text>
</body>
<body>
<text>yy</text>
</body>
<body>
<text>zz</text>
</body>
<body>
<text>kk</text>
</body>
<body>
<text>mmm</text>
</body>
</Content>
creates the desired, correct result :
<Content>
<body>
<text>xxx</text>
<text>yy</text>
<text>zz</text>
<text>kk</text>
<text>mmm</text>
</body>
</Content>
Explanation
an identification rule copies each node "as is".
Ends with two patterns. The first ignores / deletes each item body.
, , ( body) body, body . body body , body ( body body) .