I'm pretty sure what majora said is very much correct, with ura zelda being what we now know as the master quest (it's not called "master quest" in Japan, but "ura", which means "underneath"/"otherside"). Would be nice to know how all the extra content stuff turned out though, if such stuff was originally planned (although I doubt they got all that far if when they did eventually release it, as the master quest, it was only altered content to make stuff harder)