He's doing A LOT of stuff here if you view it lick by lick, but he's mostly transitioning between Harmonic Minor + Phrygian Dominant sounds. He's using Minor & Major Add 9 arpeggios & economy picked pentatonic scales too. He also goes into a straight up Major tapping lick later on.
The choice to use harmonic minor & phrygian dominant makes so much sense when you look into how A7X writes their chord progressions - they seem to love sitting on the Vb9 type sound leading to the home Minor chord. (Hail to the King Solo ending, Nightmare chorus ending, Bat Country solo ending etc)
And that seems to be a lot of what Syn's doing in the early parts of the video, basically sweeping/shredding on the V chord and keeping the crowd in suspense and then back into the Minor licks.
Theres so much more that he does but that's what I'm hearing straight away