Cannot flash from a ESP32

[modante]

Hello. I have one ESP8266 in shield format (https://www.aliexpress.com/item/ESP8266-ESP-12-ESP-12E-UART-Wifi-Wireless-Shield-Development-Board-For-Arduino-Mega-UNO-R3/32461215232.html?spm=a2g0s.9042311.0.0.348063c0jGnxHm) that I am trying to flash from a Heltec Wifi Kit 32 (ESP32 + Oled: https://www.aliexpress.com/item/ESP32-Bluetooth-WIFI-Kit-OLED-Blue-0-96-inch-Display-Module-CP2102-32M-Flash-3-3V/32826394704.html?spm=a2g0s.9042311.0.0.274263c0VXtENP)

With a simple Serial Repeater loaded on ESP32 I got to send AT Commands to the ESP8266 shield from the Serial Monitor in Arduino IDE:

void setup() {
  Serial.begin(115200);
  Serial1.begin(115200, SERIAL_8N1, 16, 17);
}
void loop() {
   if (Serial.available()) {
      Serial1.write(Serial.read());
   }
   if (Serial1.available()) {
      Serial.write(Serial1.read());
   }
}

Then I sent an AT+CIOBAUD=9600 and AT+IPR=9600 to change the baud rate and since then, I couldn't to communicate again the two devices. I read something about a bug and said that the best way is to flash again the ESP8266 firmware from factory.
I am trying to flash it using the ESP32 like bridge and loading your code on the ESP32 (to act as bridge or repeater) but doesn't work. It is a bit complicated to me understand all the code but would be great to reduce the code needed to act only as a bridge in FlashingMode. I mean to use the flash_download_tool_3.9.2 to communicate with ESP32 through the serial port and this send the flash code to the ESP8266 in FUD mode. By now I only get your code to enter in AT Mode but doesn't detects when I put the ESP8266 in FUD Mode (putting micro switches 3 and 4 to ON).
Please, if you have time, could be possible to mod the code to work only like serial repeater between the ESP32 and the ESP8266?

Thank you very much for your work :-)
Regards.