I'm afraid the Simultaneous RFID Reader Library we have is not compatible with an ESP32 due to logic translation and the ESP32's incompatibility with the SoftwareSerial library. That said, one of our fantastic users, paulvha, has several posts about a workaround that he has tested and should work to use the M6E Nano with an ESP32 but it does require using the Universal Reader Assistant software. We do not have example code to run entirely on an ESP32.
First, you may need to create a voltage divider as he describes in this post. Also, this GitHub Repository has instructions on getting the M6E to work with an ESP32.
I hope this helps you get your Simultaneous RFID Reader working with your ESP32.