Cant make 2D sprite move in one axis...

Hey,
I found a script online making a 2d sprite follow the player. It works but on the y axis as well as the x. I only want the x axis or I’d have a flying zombie. Could someone please tell me how to change this script so it’ll work on the x axis only?

using UnityEngine;
using System.Collections;

public class F : MonoBehaviour {
	public Transform target;
	public int moveSpeed;
	public int rotationSpeed;
	public int maxdistance;
	private Transform myTransform;

	void Awake()
	{
		myTransform = transform;
	}

	void Start ()
	{
		
		maxdistance = 2;
	}

	void Update () {
		if (Vector3.Distance(target.position, myTransform.position) > maxdistance)
		{
			// Get a direction vector from us to the target
			Vector3 dir = target.position - myTransform.position;
			
			// Normalize it so that it's a unit direction vector
			dir.Normalize();
			
			// Move ourselves in that direction
			myTransform.position += dir * moveSpeed * Time.deltaTime;
		}
	}
}

You can update your update function with the next code:

void Update()
{
    Vector3 targetPos = target.position;
    targetPos.y = myTransform.position.y;

    if (Vector3.Distance(targetPos, myTransform.position) > maxdistance)
    {
        // Get a direction vector from us to the target
        Vector3 dir = targetPos - myTransform.position;

        // Normalize it so that it's a unit direction vector
        dir.Normalize();

        // Move ourselves in that direction
        myTransform.position += dir * moveSpeed * Time.deltaTime;
    }
}