Problem:-
How many different 4×4 arrays whose entries are all 1's and -1's have the property that the sum of the entries in each row is 0 and the sum of the entries in each column is 0?

I tried to Fix 1,-1 on each column so that sum of each column is zero but then sum of some rows aren't zero

I'm confused how to arrange them in order to sum zero,I shall be thankful if somebody explain me the solution since i'm weak in combinatorics