void servoWrite(int pin, int angle)
{
  int duty = map(angle, 0, 180, 400, 2000);
  ledcWrite(pin, duty);
}

void setup()
{
  for (int channel = 0; channel < 4; ++channel)
  {
    ledcSetup(channel, 50, 14);
    ledcAttachPin(channel + 4, channel);
  }

  for (int angle = 90; angle > 0; --angle)
  {
    for (int channel = 0; channel < 4; ++channel)
    {
      servoWrite(channel, angle);
      delay(5);
    }
  }
}

void loop()
{
  for (int angle = 0; angle < 180; ++angle)
  {
     for (int channel = 0; channel < 4; ++channel)
    {
      servoWrite(channel, angle);
      delay(5);
    }
  }

  for (int angle = 180; angle > 0; --angle)
  {
    for (int channel = 0; channel < 4; ++channel)
    {
      servoWrite(channel, angle);
      delay(5);
    }
  }
}