Parallaxing.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Paralaxing : MonoBehaviour
{
    public Transform[] backgrounds;

    private float[] parallaxScales;

    public float smoothing;

    private Vector3 previousCameraPosition;
    // Start is called before the first frame update
    void Start()
    {

        previousCameraPosition = transform.position;

        parallaxScales = new float[backgrounds.Length];

        for (int i = 0; i < parallaxScales.Length; i++)
        {
            parallaxScales[i] = backgrounds[i].position.z * -1;
        }
    }

    // Update is called once per frame
    void LateUpdate()
    {
        for (int i = 0; i < backgrounds.Length; i++)
        {
            Vector3 parallax = (previousCameraPosition - transform.position) * ( parallaxScales[i] / smoothing);

            backgrounds[i].position = new Vector3(backgrounds[i].position.x + parallax.x, backgrounds[i].position.y + parallax.y, backgrounds[i].position.z);
        }

        previousCameraPosition = transform.position;
    }
}