Multiple simultaneous rotation changes on one object

     //Called in Update()
 
 
             float yAngle = Mathf.SmoothDampAngle(angles.y, rot.eulerAngles.y, ref velocity, minTime, core.groundcraftMovement.turnSpeed * speedMod, Time.deltaTime);
     
              Vector3 newRot = new Vector3(_transform.rotation.x, yAngle, _transform.rotation.z);

              _transform.rotation = Quaternion.Euler(newRot);
 
 
     //Called in FixedUpdate()
 
                 Vector3 temp = _transform.forward - Vector3.Dot(_transform.forward, hitNormalSum) * hitNormalSum;
     
                 Quaternion rot = Quaternion.LookRotation(temp, hitNormalSum);
     
                 _transform.rotation = Quaternion.Slerp(_transform.rotation, rot, 1 * Time.deltaTime);
 

This is from a hover tank script that can be controlled by both players and AI.

The first snippet controls AI rotation, which only affects the Y axis.

The second snippet is the hover tank adjusting to the surface normal.

How do I use both these rotation changes simultaneously without one overriding the other?