Z-order in 9 lines of C

gistfile1.c

// It only z-orders 8-bit numbers correctly but you can modify
// the for loop so that it works for more bits (maybe replace 8
// with 16 or 32, 64 is probably a bad idea unless you have a
// 128-bit system) and the return/ret and parameter type accordingly.
int zOrder( int lhs, int rhs ) {
    int bit, ret;
    for ( ret = 0, bit = 0; bit < 8; ++bit ) {
        ret |= ( ( ( lhs & 1 ) << 1 ) | ( rhs & 1 ) ) << ( bit << 1 );
        lhs >>= 1;
        rhs >>= 1;
    }
    return ret;
}