As we do not understand our own consciousness and how it functions (or whether or not it functions in me the way it does in you, if it exists at all - anywhere), we cannot compare a replication of that system to ourselves except as a black box. When seen as a black box, a philosophical zombie and a sapient individual are identical.
A black box is something we don't have access to its inner workings. We can probe and inquire the working brain. It's just really hard and we've been working at it for a few decades only (dissecting a dead brain before powerful microscopes gives you very little insight).
Unless you share the Zen-like opinion that a brain can't understand itself, which I don't, and seems like an issue of faith as well and a dead end.