If Zodiark was truly more powerful than Hydaelyn, then Hydaelyn would never have been able to defeat him. That's my main point.
Hydaelyn's original claim was that Zodiark sought to covet power for himself, though recent revelations have thrown that askew. On Hydaelyn's end, she was apparently only meant to keep Zodiark's power in check - but that wasn't what she did. She effectively destroyed him and shattered reality in the process.
Zodiark having 'more' sacrifice to fuel him doesn't necessarily equal more pure power, especially if the method to summon Hydaelyn was different and more refined. Which is exactly the sort of plot convenience I've come to expect lately.
Hopefully the writers didn't just show us Amaurot to give us another 'sad moment' and they actually plan to commit to the idea that both Zodiark and Hydaelyn are not ideal and they're very dangerous. I'd find it rather dull if there's a contrived explanation for Hydaelyn being 'necessary' but Zodiark is not.
That they have both been revealed to be Primals rather than actual deities is a step in the right direction though I'm still wary about what the future will potentially bring.
Either way, I'm also worried about Zenos being involved in all of this. He's too much of a pure plot device for me to appreciate him as a character - and he consistently does things in a way that allows for the protagonists to never really have to get their hands dirty.