Have you tried a two-pass approach? For example, where prompt #1 is "Which elliptic curves have rational parameterizations?", and then prompt #2 (perhaps to a smaller/faster model like Gemma) is "In the following text, replace all LaTeX-escaped notation with Markdown code blocks and unicode characters. For example, $F_n = F_{n - 1} + F_{n - 2}$ should be replaced with `Fₙ = Fₙ₋₁ + Fₙ₋₂`. <Response from prompt #1>". Although it's not clear how you would want more complex things to be converted.

I've done latex -> mathml -> markdown and it works quite well

It is actually quicker to ask using LaTeX markup!