unity – Enhance efficiency of three-dimensional array copy

My three dimensional array is getting so sluggish after I assign one other array to it.

SerializableQuaternion is a customized kind for saving, so it is totally different from Quaternion.

Is there a greater solution to improve the copy efficiency?

var anro = new Quaternion[60,60,60];
An = new SerializableQuaternion[anro.GetLength(0), anro.GetLength(1), anro.GetLength(2)];
saveIndex = new int[sIn.Length];
if (anro != null)
{
    for (int a = 0; a < anro.GetLength(0); a++)
    {
        for (int b = 0; b < anro.GetLength(1); b++)
        {
            for (int c = 0; c < anro.GetLength(2); c++)
            {
                An[a, b, c] = anro[a, b, c];
            }
        }
    }
}

I keep in mind I would like to make use of SerializableQuaternion to reserve it to an area file..
if not it should present error

“”SerializationException: Kind ‘UnityEngine.Quaternion’ in Meeting ‘UnityEngine.CoreModule, Model=0.0.0.0, Tradition=impartial, PublicKeyToken=null’ is just not marked as serializable.”

I saving like this

BinaryFormatter formatter = new BinaryFormatter();;
FileStream stream = new FileStream(path, FileMode.Create);

savedata knowledge = new savedata();
formatter.Serialize(stream, knowledge);

my customized kind

[System.Serializable]
public struct SerializableQuaternion
{
    public float x;

    public float y;

    public float z;

    public float w;

    public SerializableQuaternion(float rX, float rY, float rZ, float rW)
    {
        x = rX;
        y = rY;
        z = rZ;
        w = rW;
    }

    public override string ToString()
    {
        return String.Format("[{0}, {1}, {2}, {3}]", x, y, z, w);
    }

    public static implicit operator Quaternion(SerializableQuaternion rValue)
    {
        return new Quaternion(rValue.x, rValue.y, rValue.z, rValue.w);
    }

    public static implicit operator SerializableQuaternion(Quaternion rValue)
    {
        return new SerializableQuaternion(rValue.x, rValue.y, rValue.z, rValue.w);
    }
}