So, I have learned about cofactor expansion. But the cofactor expansion I know doesn't reduce the number of rows and colums to one matrix. I usually pick a colum, multiply each element in the column by its determinant. I also know that you can factor rows, but I don't see how it could be done here. Help me, Atleast get me off step-1;
Notice that if you apply the cofactor expansion along the first column we have a lot of zeroes so we only need to worry about $3$ multiplied by the determinant of a smaller matrix. Notice that there is another candidate column to which to apply the cofactor expansion in the smaller matrix (the column with the most zeroes). Continue this process. Notice that this will not be too difficult in computing since most of the expansion involves multiplication by $0$.