I mean think about it, they both supposedly are balance to each other in a way, Hydalin won and banished Zodiark, shatterign him in pieces, i doubt there even is a full Zodiark anymore if only remains like with Elidibus. The thing here is, we kept beating the Ascians over and over, we prevent another calamity even, beaten Primae after Primae not always resummoned anymore. Yet she still is supposedly in a weak state and Zodiark who was in pieces gets stronger? This all smells simply fishy to me.
I start to believe Zenos will get Hydalin instead, and Zodiark will even add to our help in some way. Hydalin is to quote Gaius, also just a parasite like the other Primae and gods honestly. Hydalin i fear will turn out more worse then we believe so farm, if you tihnk about it she might be the basic embodiments of an Ascian, the same people that made her, manipulating people and telling lies.
What makes me think that? Well, as we seen with Elidibus repeating the Starfall twice and, "Hydalin" spoken to people, it makes me think Hydalin might never truely speaken to us or at least not all the time. Thing is also with her supposed weakened state, so many believe in Hydalin and Elidibus shown they can take this beleive as power, so why doens't Hydalin get stronger? While Zodiark, this "long ago sealed away evil" basically with no one knowing even the full truth.
Same for the other gods even, Urianger himself after the last Quest in the sieroom says he starts to question The Twelves origins. This will surely lead to something i say, and honestly i will be happy if Hydalin will not just be the untouchable holy being anymore, considering the peopels believe in her are even more blind then the Ascians had to Zodiark.
Zodiark and Hydalin both are Primae, they see each other as rival same for other primae, it is in there nature simply. Something no one of them can hide, if it is true, then she is the biggest parasite of them all, sucking on the worlds essence since it splitted apart to keep herself going. Ironically that reminds me of the Legacy of Kain series. the Elder God, a parasite posing as a god of Death and Rebirth, while in reality consuming the Souls of the land to feed his hunger, hurting the world in the end and even blaming others for its state.
This would honestly be a good plot twist in my eyes. And not just another Good vs Evil with no grey areas at all, which we gladly had alot, more recent with Elidibus and Emet Selch, only wished they had stayed longer, even Lahabrea.
Main point what worrys me is simply how we not hear anything about her anymore, no medium like Minfillia (thnak god she is hopefully gone for good) used to talk to us even, it feels liek she got caught honestly with the whole Primae oiginof her and Zodiark.