Unless you just made a large number of typos posting this code, your indexing is sloppy; some of the array elements aren't initialized, some are overwritten and at one point you index out of bounds of the array. That looks like your problem.

Unless you just made a large number of typos posting this code, your indexing is sloppy; some of the array elements aren't initialized, some are overwritten and at one point you index out of bounds of the array. That looks like your problem.

m[0][0] = 2 / (right - left);   
    m[0][1] = 0;                        
    m[0][2] = 0;                        
    m[0][3] = 0;

    m[1][0] = 0;                        
    m[1][2] = 2 / (top - bottom); // should probably be m[1][1]
    m[1][2] = 0;                  // immediately overwrites m[1][2]
    m[1][3] = 0;

    m[2][0] = 0;                        
    m[2][3] = 0;                  // should probably be m[2][1]
    m[2][2] = -1 / (zFar - zNear);  
    m[2][3] = 0;                  // again overwrites m[2][3]

    m[3][0] = -(right + left) / (right - left);
    m[3][4] = -(top + bottom) / (top - bottom); // m[3][4] is out of bounds of the array
    m[3][2] = -zNear / (zFar - zNear);
    m[3][3] = 1;