<<< native
[ EArray
    [ AlignCenter ]
    [ [ [ EGrouped
            [ EPhantom (EText TextNormal "fail")
            , EIdentifier "H"
            , EPhantom (EText TextNormal "fail")
            ]
        ]
      ]
    , [ [ EIdentifier "T" ] ]
    , [ [ EIdentifier "U" ] ]
    ]
, ESymbol Rel "="
, EArray
    [ AlignCenter ]
    [ [ [ EIdentifier "H" ] ]
    , [ [ EIdentifier "T" ] ]
    , [ [ EGrouped
            [ EPhantom (EText TextNormal "fail")
            , EIdentifier "U"
            , EPhantom (EText TextNormal "fail")
            ]
        ]
      ]
    ]
]
>>> tex
\begin{matrix}
{\phantom{\text{fail}}H\phantom{\text{fail}}} \\
T \\
U
\end{matrix} = \begin{matrix}
H \\
T \\
{\phantom{\text{fail}}U\phantom{\text{fail}}}
\end{matrix}