Native SDK with WIO 2040

Hi

I wonder if there is information about the internal connections between the RP2040 and the ESP8266 that I presume are the Wio 2040.

I would like to use the RPI SDK and the esp-idf respectively in order to do some lower level programming, so in addition to the RP2040 programming that I guess is pretty obvious by burning a new uf2 image, I would like to know how to flash the internal ESP8266 as well.

Is there any place to start reading? thank you