Zoecite was a dude in the anime also, it is just they change him to a girl in the dubbed.

Anyways Neflite is from Earth, as we already established he was a guardian of Prince Endymion. Though he could be from another planet like Kaitou Ace (Adonis was his real name right?), there has not been, as far as I remember, any evidence to show that Neflite is from the Moon. Also this happens solely in the anime for Neflite does not live long enough to know Molly (I forget her original name) well enough.

Yes there is a taboo against the coupling of those from the Moon and Earth. See people of the Moon live longer, thus making normal Earthlings jealous. Another reason is because those of the Silver Millenium are intrusted to guard the Earth. Princess Selenity broke this taboo, which she then paid for with her life. Well after Prince Endymion got killed, she used the sword meant to protect her to commit suicide upon. (She also died in the anime by the hands of Beryl which her actions could be seen as suicidal, but it is much more evident in the manga). Well this is all according to the manga, which has been a while since I read.