<<< native
[ ESubsup (EIdentifier "V") (EIdentifier "m") (EIdentifier "n")
, ESymbol Rel "="
, EUnderover
    False
    (ESubsup (EIdentifier "V") (EIdentifier "m") (EIdentifier "n"))
    (EPhantom (EText TextNormal "d"))
    (EPhantom (EText TextNormal "d"))
]
>>> eqn
V sub m sup n = {V sub m sup n} from {hphantom {roman "d"}} to {hphantom {roman "d"}}