Right, remember the bullets from the speed section? Well before he gets his head in the game and starts catching them, Zeon takes a fair few hits. Before I show the hits and the damage it does to him, a little context.
These bullets are capable of blasting straight through Zeon's building busting lightning attacks with no problem. Please note the strength it shows that Zeon is able to catch these bullets with his bare hands like it's nothing. This scan is also a nifty speed feat, even though he's surprised, Zeon still reacts and raises his arms to block the bullet when it's like a metre and a half from him. Also, durability, note how he's only bleeding a little bit and otherwise unhurt.
Now, I know what you're thinking; "But Nik, that bullet has just blasted through a building busting level lightning storm. Surely it would have lost some of its energy so Zeon would be less hurt,"
That is a good point. So allow me to counter with Zeon getting shot in the arm by surprise. Note that there he's more surprised than hurt.
He then proceeds to use the strategy of tank the bullets to triangulate their origin. Note how he's only superficially bleeding here. His fighting ability is utterly unaffected by the hits. Even then he takes another hit he's totally unprepared for and is only superficially hurt.
Here's the sum damage done to him when being hit by a Dioga Class Spell that explicitly did nothing to defend against: Scratch Zero. Zeon is ridiculously durable.
He also wears a mantle that is even more absurdly durable than he is. He can also manipulate it's shape with his mind. Wrapping an ordinary human in it allows him to survive a vastly powered up Baoh Zakeruga attack with no damage. He can also use it to bounce Gigano class spells with no effort.
Even taking Baoh Zakeruga to the face deliberately, isn't enough to kill him. It just knocks him out for about 30 seconds and hurts him enough that he's immobilised.
So yeah, incredibly durable. Tanks building buster+ attacks with no damage and hits from attacks that blow through said building buster+ level attacks with only superficial bleeding. In fact, throughout the manga, Zeon is only ever significantly hurt by Baoh Zakeruga, which is arguably the strongest spell in the series.
Lastly, we'll be doing an overview of Zeon's Techniques of which he has many.