I have heard somewhere (but it probably is in the instruction book) that in
AoL, they decided that all princesses in the royal family would be named Zelda.
This makes one belive it's the first part of Zelda. But there is a theory by me, which I belive to make sense.
In
LoZ, which comes before
AoL, whole Hyrule is just nature. You see humans, but you don't see a town, or houses. Just caves, bushes, tree's, lakes. So in some way, Hyrule must have been destroyed, maybe again.
So in this way, the royal family belives in
AoL that they are the first kingdom, and decides somehow to name all the following princesses Zelda.
But I might be wrong, some part of the story may prove this...