Look. Suppose I made a copy of you who was a zombie. He acted like you in every way, but he had no experiences, no qualia, etc.
Would he believe he was a zombie? No. He'd be just like you: he'd insist that qualia are real, that he is having an undeniable internal experience right now, etc. If I asked that zombie "how do you know you're not a zombie?" what would he tell me?
-unless you love someone-
-nothing else makes any sense-