Okay, so you're asking about the reading order for 'Zodiac Academy' after Book 2, which usually means the 'Ruthless Fae' series and the spin-offs. It gets a little messy.
The core series is straightforward: just keep going with 'Zachary' and 'The Reckoning'. But where it gets fun is with 'The Awakening As Told By The Boys', which is 'The Awakening' (book 1) from the Heirs' perspective. You can read it anytime after book 1, but a lot of fans, myself included, think slotting it in right after you finish 'The Awakening' enriches everything that comes after because you get all their motivations upfront.
Then there's 'Dark Fae', the first book of the 'Ruthless Boys of the Zodiac' series. It's a prequel set five years before ZA, with different characters. You can start it after ZA book 2, or even after book 1, honestly. It's a separate story but set in the same world, and it explains a ton about the world's politics and some familiar families. I jumped into it after ZA2 and didn't feel lost at all; it was a nice breather from Tory and Darcy's drama.
So my suggested order would be: ZA1, 'As Told By The Boys', ZA2, then 'Dark Fae' (Ruthless Boys #1). After that, you can either continue with Ruthless Boys or go back to ZA3. I mixed them and liked seeing the connections pop up.