<<< native
[ EFraction
    NormalFrac
    (EFraction NormalFrac (EIdentifier "a") (EIdentifier "b"))
    (EFraction NormalFrac (EIdentifier "c") (EIdentifier "d"))
, ESymbol Rel "="
, EFraction
    NormalFrac
    (EFraction NormalFrac (EIdentifier "a") (EIdentifier "b"))
    (EFraction NormalFrac (EIdentifier "c") (EIdentifier "d"))
]
>>> tex
\frac{\frac{a}{b}}{\frac{c}{d}} = \frac{\frac{a}{b}}{\frac{c}{d}}