I have a requirement ,as below, in XSLT

A sample xml input replicating my actual scenario.

<Root>
    <List1>
        <list1Child>
            <Id>1</Id>
            <Name>Test1</Name>
        </list1Child>
        <list1Child>
            <Id>2</Id>
            <Name>Test2</Name>
        </list1Child>
    </List1>

    <List2>
        <list2Child>
            <AoId>1</AoId>
            <Department>Dep1</Department>
        </list2Child>
        <list2Child>
            <AoId>1</AoId>
            <Department>Dep11</Department>
        </list2Child>
        <list2Child>
            <AoId>2</AoId>
            <Department>Dep2</Department>
        </list2Child>
    </List2>

</Root>

Here, I would want the List2 elements to appear as nested elements under list 1.Here Id and AoId are matching keys

Sample output below

<Root>
    <List1>
        <list1Child>
            <Id>1</Id>
            <Name>Test1</Name>
            <List2>
                <list2Child>
                    <AoId>1</AoId>
                    <Department>Dep1</Department>
                </list2Child>
                <list2Child>
                    <AoId>1</AoId>
                    <Department>Dep11</Department>
                </list2Child>
            </List2>
        </list1Child>
        <list1Child>
            <Id>2</Id>
            <Name>Test2</Name>
            <List2>
                <list2Child>
                    <AoId>2</AoId>
                    <Department>Dep2</Department>
                </list2Child>
            </List2>
        </list1Child>
    </List1>
</Root>

I am using XSLT (version 2) and was able to do this with nested for-each loop and predicates. Snippet of the pseudocode provided below

<xsl:stylesheet version="2.0">
<xsl:template match="/">
<xsl:for-each select="/Root/List1/list1Child">

..
..
..
<xsl:for-each select="/Root/List2/list2Child [AoId=Id]">

..
..
..
</xsl:for-each>
</xsl:for-each>

</xsl:template>
</xsl:stylesheet>

However, in certain cases, I have a very large xml and this xslt takes around 10 seconds. I would want to improve performance. I thought using keys might improve the performance and tried the below

<xsl:stylesheet version="2.0">
<xsl:key name="List2Key" match="list2Child" use="AoId"/>

<xsl:template match="/">
<xsl:for-each select="/Root/List1/list1Child">

..
..
..
<xsl:for-each select="key(‘List2Key’,Id)">
..
..
..
</xsl:for-each>
</xsl:for-each>

</xsl:template>
</xsl:stylesheet>

However the above fails to get parsed. Maybe the key is of a different node and is probably not getting recognized under the first for-each node? I tried to use for-each-group and Muenchian Method. However couldn’t get that to work.Is there any other more efficient way to achieve this nested structure. Appreciate any directions for the effective solution.