<<< omml
<?xml version="1.0" encoding="UTF-8"?>
<m:oMathPara>
  <m:oMathParaPr>
    <m:jc m:val="center" />
  </m:oMathParaPr>
  <m:oMath>
    <m:borderBox>
      <m:e>
        <m:sSup>
          <m:e>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>x</m:t>
            </m:r>
          </m:e>
          <m:sup>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>2</m:t>
            </m:r>
          </m:sup>
        </m:sSup>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>+</m:t>
        </m:r>
        <m:sSup>
          <m:e>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>y</m:t>
            </m:r>
          </m:e>
          <m:sup>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>2</m:t>
            </m:r>
          </m:sup>
        </m:sSup>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>+</m:t>
        </m:r>
        <m:sSup>
          <m:e>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>z</m:t>
            </m:r>
          </m:e>
          <m:sup>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>2</m:t>
            </m:r>
          </m:sup>
        </m:sSup>
      </m:e>
    </m:borderBox>
  </m:oMath>
</m:oMathPara>

>>> native
[ EBoxed
    (EGrouped
       [ ESuper (EIdentifier "x") (ENumber "2")
       , ESymbol Bin "+"
       , ESuper (EIdentifier "y") (ENumber "2")
       , ESymbol Bin "+"
       , ESuper (EIdentifier "z") (ENumber "2")
       ])
]