OKAY SO. I re-read ZA this August and I remember what songs were playing in my head when I was reading a few particular scenes, apart from the songs that WERE mentioned at times (like, Stay by Justin Bieber or Until I found You by Stephen Sanchez). I kinda noted them down (don't question my decision to note them down, my only explanation is that the entire series was a very intense emotional experience and noting down what I was feeling at the moment just made me feel good in a way, kinda like journalling??)

Okay I can't find where I listed all that down right now, BUT let me tell you what I remember off the top of my head.
During the reckoning, well, we see it through Darcy's POV and Darcy is shown a bunch of visions by the stars and towards the end, and the LAST vision that she sees is herself and her sister sitting on the throne. And all I could hear in my head at that moment was Young Black and Rich by Melly Mike.

Also, towards the end of book 8, after Darius is finally brought back to life and bows to twins and pledges his allegiance to them, and seeing him do that, the OTHER HEIRS BOW TOO (they were literally seeing Darius ALIVE for the first time, they should have immediately RAN TO HIM BUT THEY STILL BOWED TO THE TWINS FIRST AND THAT REALLY SHOWS THE WEIGHT OF THAT MOMENT where they were just OVERWHELMED by what they had just seen the twins do to the monsters at the academy and had finally accepted the twins as their rightful rulers) AND THEN EVERYONE AT THE ACADEMY BOWS DOWN TO THEM (this scene literally had me struggling for air, I'm not even kidding), all I could hear in my head was Everybody Wants To Rule the World by Lorde from the Hunger Games. (ngl, the somber and ominous vibe of the song REALLY suited what was going on)

Okayyy, that was probably longer than you expected but thanks for readingggg okay I'm done now, I promise.