Finding this a bit of a slog, I'm afraid. I have a lot of the untransmuted answers, but struggling with the many possible substitutions.
Would I be right in thinking that 4 down and 16 across are remarkably similar? Or am I on completely the wrong track?
(Apologies to anyone not doing this crossword - there is no point in me just giving the clues to these without also spelling out the rules and that would be too complicated. The Genius is available online at The Guardian)