Enemies vibrate along Z axis

1. I'm making a 3D game with the camera set to orthograp$$anonymous$$c to keep movements and boundaries simple.

2. When my player moves (using AddForce), it appears to move much slower when moving vertically (Z axis) than horizontally (X axis), because of the camera angle. I fixed t$$anonymous$$s by adding a vertEnhancer variable to multiply in the AddForce equation. It works pretty well, multiplying all vertical movements by 2.

3. I just learned how to move enemies toward the player by using "enemyRB.AddForce((playerPos - enemyPos) * enemySpeed);". T$$anonymous$$s works, but I'm left with the slower vertical movements unless I can apply the same vertEnhancer to ONLY the Z movement, but that's not possible without atomizing the formula.

4. So I did. I spent like two days figuring out how to parse (playerPos - enemyPos) into individual coordinates, and ended up with what you see below. Now it works almost perfectly!! EXCEPT--when it moves in a pure vertical direction, it shakes, ever so slightly, but it's weird. And I really don't even know where to start to fix that. It doesn't happen when they move diagonally, and it does happen whether or not I include the vertEnhancer.

5. Any ideas??

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PLAYER MOVEMENT (WORKS GREAT):

     void Update()
         {
             //Movement
             float horizontalInput = Input.GetAxisRaw("Horizontal");
             float verticalInput = Input.GetAxisRaw("Vertical");
             float vertEnhancer = 2;
             
             playerRB.AddForce(Vector3.forward * playerSpeed * vertEnhancer * verticalInput, ForceMode.Impulse);
             playerRB.AddForce(Vector3.right * playerSpeed * horizontalInput, ForceMode.Impulse);
     
     

ENEMY MOVEMENT (AS THE TUTORIAL TAUGHT):

 void Update()
             {
                 //Movement
                 Vector3 enemyVector = (player.transform.position - transform.position).normalized;
         
                 enemyRB.AddForce(enemyVector * enemySpeed);
             }

ENEMY MOVEMENT (ATOMIZED FOR APPLYING vertEnhancer):

 void Update()
             {
         
                 //Movement
                 float playerPosX = player.transform.position.x;
                 float playerPosZ = player.transform.position.z;
         
                 float enemyPosX = transform.position.x;
                 float enemyPosZ = transform.position.z;
         
                 float vertEnhancer = 2;
         
                 Vector3 enemyVectorVert = new Vector3(0, 0, playerPosZ) - new Vector3(0, 0, enemyPosZ);
                 Vector3 enemyVectorHori = new Vector3(playerPosX, 0, 0) - new Vector3(enemyPosX, 0, 0);
         
         
                 enemyRB.AddForce(enemyVectorVert.normalized * enemySpeed * vertEnhancer, ForceMode.Impulse);
                 enemyRB.AddForce(enemyVectorHori.normalized * enemySpeed, ForceMode.Impulse);