Idea:

Use direct port/pin control:

#define MOTOR1_PIN1 9
#define MOTOR1_PIN2 10
#define MOTOR2_PIN1 11
#define MOTOR2_PIN2 12

void setup() {
// Other stuff
  pinMode(MOTOR1_PIN1, OUTPUT);
  pinMode(MOTOR1_PIN2, OUTPUT);
  pinMode(MOTOR2_PIN1, OUTPUT);
  pinMode(MOTOR2_PIN2, OUTPUT);
// More stuff
}

void loop() {

  int motor1Speed = // data
  int motor2Speed = // data

  controlMotor1(motor1Speed);
  controlMotor2(motor2Speed);

  delay(40);
}

// Create two new functions to handle motor control

void controlMotor1(int speed) {
  // Set the direction of motor 1 based on the speed
  if (speed >= 0) {
    digitalWrite(MOTOR1_PIN1, HIGH);
    digitalWrite(MOTOR1_PIN2, LOW);
  } else {
    digitalWrite(MOTOR1_PIN1, LOW);
    digitalWrite(MOTOR1_PIN2, HIGH);
    speed = -speed; // Make the speed positive for analogWrite
  }

  analogWrite(MOTOR1_PIN2, speed);
}

void controlMotor2(int speed) {

  if (speed >= 0) {
    digitalWrite(MOTOR2_PIN1, HIGH);
    digitalWrite(MOTOR2_PIN2, LOW);
  } else {
    digitalWrite(MOTOR2_PIN1, LOW);
    digitalWrite(MOTOR2_PIN2, HIGH);
    speed = -speed; // Make the speed positive for analogWrite
  }

  analogWrite(MOTOR2_PIN2, speed);
}

// Rest of program