"One country" is the snake's body, and its two heads are the two systems. It is not workable, even in principle. Add to this mainland China's bungling approach and corrupt legal system, and the chances of success are remote, to say the least!
一國兩制好比兩頭蛇，「一國」是蛇身，兩蛇頭分別是兩制，原理上實不可行，加上大陸人謀不臧，法治敗壞，成功難於登天矣！