(noob) 2 servos for robot (head & chest) movement at different speeds at once
Heres a little sketch you can try.  It uses timing to accomplish the different servo speeds.  It won't give you the exact servo travel each loop but it sounds like you might not mind if it randomly is off by a few degrees each loop.
#include &lt;Servo.h&gt;
Servo servo1;
Servo servo2;
int i = 0;
void setup() {
  Serial.begin(9600);
  servo1.attach(8); 
  servo2.attach(9); 
} 

int sweep_time = 3500; // 70 * 50ms = 3500

int head_degrees = 75; // sweep degrees for the head to move
int body_degrees = 65; // sweep degrees for the body to move

int millis_per_head_move = sweep_time / head_degrees;
int millis_per_body_move = sweep_time / body_degrees;

void loop() {
  int i = 0; int j = 0;
  unsigned long now_millis = 0;
  unsigned long start_sweep = millis(); // mark the time when we start the first sweep
  
  while ( millis() - start_sweep &lt; sweep_time ) {  // keep moving first sweep until sweep time has elapsed
    now_millis = millis() - start_sweep;
    if (now_millis % millis_per_head_move == 0 ) servo1.write(i++);
    if (now_millis % millis_per_body_move == 0 ) servo2.write(j++);
    delay(1);
  }
  Serial.print(i); Serial.print(&quot; &quot;); Serial.println(j);
  
  start_sweep = millis();  // mark the time when we start the second/back sweep
  while ( millis() - start_sweep &lt; sweep_time ) {  // keep moving second sweep until sweep time has elapsed
    now_millis = millis() - start_sweep;
    if (now_millis % millis_per_head_move == 0) servo1.write(i--);
    if (now_millis % millis_per_body_move == 0) servo2.write(j--);
    delay(1);
  }
  Serial.print(i); Serial.print(&quot; &quot;); Serial.println(j);
}