I see nothing there that goes beyond some basic corner pin tracking and masking.
What is corner pin tracking?
I don't think it was corner pin tracking because that would have required Zach to actually do some slight of hand. I think the card was inserted later. My reasoning:
Shoot card front and back while watching playback of master shot so you can get timing right
Edit card shot so it looks like card flips
Roto Card (of if shot against green screen Key)
Attach card to hand using tracking data
Add mask for two fingers
Time remap card to match timing of master shot
Better... Add card shadow to shot so the give away is not so obvious
BTW, not talking about camera tracking, just simple point tracking and only for the frames where the hand is stable. EZ as pie if you can shoot and light.
Every one of his tricks require a good knowledge of lighting, good camera work, preproduction planning and good compositing skills. The tricks sell because this guy has very good tracking skills.