Нужны объяснения к коду operator * - C#

using System;
 
class Program
{
    static void Main(string[] args)
    {
        MyArray array = new MyArray(new int[] { 1, 2, 3, 4, 5 });
        MyArray array2 = new MyArray(new int[] { 6, 7, 8, 9, 10, 11, 12 });
        Console.WriteLine(array * array2);
        Console.ReadKey();
 
    }
}
 
class MyArray
{
    int[] array;
    public int Length {get; private set;}
 
    public MyArray() { }
 
    public MyArray(int size)
    {
        Length = size;
        array = new int[size];
        array.Initialize();
    }
 
    public MyArray(params int[] elements) : this(elements.Length)
    {
        Array.Copy(elements, array, elements.Length);
    }
 
    public int this[int index]
    {
        get 
        {
            return array[index];
        }
        set
        {
            array[index] = value;
        }
    }
 
    public static int? operator *(MyArray a1, MyArray a2)
    {
        int? mul = null;
        for (int i = 0; i < a1.Length; i++)
            if (a1[i] % 2 == 0)
                mul = mul == null ? a1[i] : mul * a1[i];
        for (int i = 0; i < a2.Length; i++)
            if (a2[i] % 2 == 0)
                mul = mul == null ? a2[i] : mul * a2[i];
        return mul;
    }
}