def _fast_cross_nd_sum(a, b, c):
 return (((((a[..., 1] * b[..., 2]) - (a[..., 2] * b[..., 1])) * c[..., 0]) + (((a[..., 2] * b[..., 0]) - (a[..., 0] * b[..., 2])) * c[..., 1])) + (((a[..., 0] * b[..., 1]) - (a[..., 1] * b[..., 0])) * c[..., 2]))

def _fast_cross_nd_sum ( a , b , c ) : return ( ( ( ( ( a [ ... , 1 ] * b [ ... , 2 ] ) - ( a [ ... , 2 ] * b [ ... , 1 ] ) ) * c [ ... , 0 ] ) + ( ( ( a [ ... , 2 ] * b [ ... , 0 ] ) - ( a [ ... , 0 ] * b [ ... , 2 ] ) ) * c [ ... , 1 ] ) ) + ( ( ( a [ ... , 0 ] * b [ ... , 1 ] ) - ( a [ ... , 1 ] * b [ ... , 0 ] ) ) * c [ ... , 2 ] ) )
fast cross and sum .