1. The problem is to find matrices $M$ and $N$ that are maximal square submatrices of a given matrix $C$ with nonzero determinants. 2. A maximal square submatrix means the largest possible square submatrix within $C$ that has a nonzero determinant. 3. To solve this, we need the matrix $C$ to identify all square submatrices. 4. For each square submatrix, calculate the determinant. 5. Select the largest submatrix (in terms of size) with a nonzero determinant as $M$ and $N$. 6. Without the explicit matrix $C$, we cannot compute $M$ and $N$. 7. Please provide matrix $C$ to proceed with finding $M$ and $N$.