Help understanding slower read

[NickGuyver]

When I did some testing with the below sketch I get results that don't make sense to me. These results are from a teensy 4.1 underclocked to 24MHz.

Can you please help me understand why the adc->adc0->analogRead() alternating is nearly half the speed of analogRead() when including your library?

1 - Standard analogRead() - 91us
2 - #include adc.h using adc->adc0->analogRead() and adc->adc1->analogRead() - 31us
3 - #include adc.h using analogRead() - 19us

#include <ADC.h>
#include <ADC_util.h>

unsigned long start = 0;
unsigned long stop = 0;

int readPin0 = A0;
int readPin1 = A1;
int readPin2 = A2;
int readPin3 = A3;

ADC *adc = new ADC();

void setup() {

  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(readPin0, INPUT_DISABLE);
  pinMode(readPin1, INPUT_DISABLE);
  pinMode(readPin2, INPUT_DISABLE);
  pinMode(readPin3, INPUT_DISABLE);

  Serial.begin(9600);

  ///// ADC0 ////
  adc->adc0->setAveraging(0);  // set number of averages
  adc->adc0->setResolution(10); // set bits of resolution
  adc->adc0->setConversionSpeed(
      ADC_CONVERSION_SPEED::VERY_HIGH_SPEED); // change the conversion speed
  adc->adc0->setSamplingSpeed(
      ADC_SAMPLING_SPEED::VERY_HIGH_SPEED); // change the sampling speed

  ////// ADC1 /////
  adc->adc1->setAveraging(0);  // set number of averages
  adc->adc1->setResolution(10); // set bits of resolution
  adc->adc1->setConversionSpeed(
      ADC_CONVERSION_SPEED::VERY_HIGH_SPEED); // change the conversion speed
  adc->adc1->setSamplingSpeed(
      ADC_SAMPLING_SPEED::VERY_HIGH_SPEED); // change the sampling speed

  delay(500);
}

int value1 = 0, value2 = 0, value3 = 0, value4 = 0;
int pin = 0;

void loop() {
  start = micros();
  
  //value1 = adc->adc0->analogRead(readPin0);
  //value2 = adc->adc1->analogRead(readPin1);
  //value3 = adc->adc0->analogRead(readPin2);
  //value4 = adc->adc1->analogRead(readPin3);

  value1 = analogRead(readPin0);
  value2 = analogRead(readPin1);
  value3 = analogRead(readPin2);
  value4 = analogRead(readPin3);
  
  stop = micros() - start;
  
  Serial.println();
  Serial.print("time - ");
  Serial.print(stop);
  Serial.println();
  
  Serial.print(value1);
  Serial.print(", ");
  Serial.println(value2);
  Serial.print(value3);
  Serial.print(", ");
  Serial.println(value4);
  Serial.println();
  delay(200);
}