Zelda turns into the light dragon for she has the power of light and time light was stronger in her so she turned into the light dragon. tell me anything you think about this for this is my first theory. I'll ad more info to this when I think of it
This is a great theory! Zonai are said to be descended from the gods, and dragons throughout the series have been shown to be as close as you can get to godhood (in Skyward Sword and Wind Waker). The three dragons must have had secret stones (presumably for fire, ice and lightning), which means there must be more than seven secret stones. There are also three Dark Leviathan skeletons below the Leviathans that look have the same type of lengthy dragon body; perhaps these were also Zonai? Finally, there is the Zonai god who gifted the Rito the Stormwind Ark.
This gives us 9 known Zonai:
Rauru: Light
Mineru: Spirit
Dinraal: Fire
Naydra: Ice (water?)
Farosh: Lightning
Eldin Dark: ???
Hebra Dark: ???
Gerudo Dark: ???
Stormwind: Wind
The missing Zelda sage elements are forest, shadow, time, and earth/snow. Lightning is either filling in for shadow or earth/snow in TotK. Perhaps the Dark Leviathans were the forest, shadow and time Zonai?
I'm not a fan of the idea. Heck, I wasn't a fan of Zelda's transformation in Totk. The game spends half its flashbacks talking about how you can't turn back if you eat your magic pebble and turn into a dragon, but then the game just... has the Zonai turn her back without any explanation as to how. It makes the dragon's look especially silly if they could have been changed back at any time.
I'm pretty sure it's either recall or a Triforce wish.