how to run 2 different servo (continuous rotation and regular servo) in parallel, not run one after other?
I am proposing one answer
https://wokwi.com/arduino/projects/297646292038844936
Here, we are not using the delay function. We are using the millis()
Based on your actual application, you can control individual servo accordingly.
Here is the Arduino simulation:
https://wokwi.com/arduino/projects/297646292038844936

/* Sweep
  by BARRAGAN &lt;http://barraganstudio.com&gt;
  This example code is in the public domain.

  modified 8 Nov 2013
  by Scott Fitzgerald
  http://www.arduino.cc/en/Tutorial/Sweep
*/

#include &lt;Servo.h&gt;

Servo myservo;  // create servo object to control a servo
Servo myservo2;  // create servo object to control a servo

// twelve servo objects can be created on most boards
unsigned long previousMillis = 0;        // will store last time LED was updated
const long interval = 15;           // interval at which to blink (milliseconds)

int pos = 0;    // variable to store the servo position
int pos2 = 0;    // variable to store the servo position

void setup() {
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  myservo2.attach(10);  // attaches the servo on pin 9 to the servo object

}

void loop() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis &gt;= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;


    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    pos = pos + 1;
    if (pos &gt; 180) {
      pos = 0;
    }                      // waits 15ms for the servo to reach the position

    myservo2.write(pos2);              // tell servo to go to position in variable 'pos'
    pos2 = pos2 + 1;
    if (pos2 &gt; 90) {
      pos2 = 0;
    } 



  }


}