texmath-0.12.5: test/roundtrip/msubsup-06.native

[ ESubsup
    (EIdentifier "X")
    (ESubsup (EIdentifier "Z") (ENumber "4") (ENumber "3"))
    (ESubsup (EIdentifier "Y") (ENumber "2") (ENumber "1"))
, ESymbol Rel "="
, ESubsup
    (EIdentifier "X")
    (ESubsup (EIdentifier "Z") (ENumber "4") (ENumber "3"))
    (ESubsup (EIdentifier "Y") (ENumber "2") (ENumber "1"))
]