<<< native
[ ESubsup (EIdentifier "D") (EIdentifier "x") (ENumber "2")
, ESymbol Rel "="
, ESubsup
    (EIdentifier "D")
    (EUnder False (EIdentifier "x") (EPhantom (ENumber "0")))
    (EOver False (ENumber "2") (EPhantom (ENumber "0")))
]
>>> tex
D_{x}^{2} = D_{\underset{\phantom{0}}{x}}^{\overset{\phantom{0}}{2}}