The solution for the Demonstration for the Magic Square 6x6 . These sizes are not divided by 4.
Tow lines remain.
So, divide the square into areas shown below. Consider the boundary block as the boundary line. Applying the solution of the multiple of 4 to the areas marked A to I, fill in the boxes. The sum of the empty boxes of each row or column has to be the number around the square. Let's match sums by switching some numbers in 4 blocks.