Meaning of zrewanżować in this context

On this postcard: leonidhurwicz.org/postcard-from-kaunas/

There is this sentence:

Jak wiadomo - to tylko ja jestem specjalista od odczytywania nie czytanego pisma, jak np. Twoje - a Ty nawet nie chcesz się zrewanżować.

I think I get the general sense of it:

As known - it's just me I am a specialist in reading an unread letter, such as yours - and you do not even want to (do anything at all).

In other words, "I even decipher your meaning when you don't write to me, while you can't be bothered to do anything at all."

Is that basically correct? Or what is the meaning of zrewanżować in this context?

As known - I am a specialist in reading of illegible texts, such as yours - and you don't even want to requite me (return a favor to me).

I'd say it's nieczytelnego pisma -illegible handwriting.

@Nathans
Thank you!
So the sense would be, "I read your illegible letters, but you don't seem to want to read my illegible letters. (Which I'm deducing from the fact that you never answer me.)"

??