Here are a few more functions for manipulating matrices.
void EZ_CopyMatrix(EZ_Matrix des, EZ_Matrix src);
void EZ_CopyTransposeMatrix(EZ_Matrix des, EZ_Matrix src);
void EZ_IdentityMatrix(EZ_Matrix mtx);
void EZ_ZeroMatrix(EZ_Matrix mtx);
void EZ_InvertMatrix4_(EZ_Matrix ans, EZ_Matrix src, int transp);
void EZ_World2Screen(float *xyz, int *x, int *y, float *fz);
void EZ_Screen2World(int x, int y, float *fx, float *fy);