using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<List<int>> list1 = new() { new() { 1, 2 }, new() { 3, 4 }};

        List<List<int>> list2 = new() { new() { 2, 1 }, new() { 4, 3 }};

        List<List<int>> list3 = new() { new() { 3, 4 }, new() { 1, 2 }};

        List<List<int>> list4 = new() { new() { 4, 3 }, new() { 2, 1 }};

        List<List<int>> squareCombined = list1

            .Zip(list2, ( el1, el2 ) => el1.Concat(el2).ToList())

            .Concat(list3

                .Zip(list4, ( el3, el4 ) => el3.Concat(el4).ToList()))

            .ToList();

        foreach (var combinedList in squareCombined)

        {

            Console.WriteLine(string.Join(" ", combinedList));

        }

    }

}