We are not talking about Gluttony. If you want, I'll make a Greed vs Gluttony thread.
The whole point of the Ultimate Shield is that it is impossible to break. That was why Edward couldn't hurt him and Izumi couldn't either. Until with their alchemy, they took it away.
The whole point of the first Wrath vs Greed fight was that Wrath used his Ultimate Eye to see Greed's weakness. Greed can't heal and harden at the same time. So, Wrath attacked Greed before Greed had a chance to harden himself. Once Wrath first cut his arm off, it was over.
If Wrath could have bypassed his Ultimate Shield, he would have done so. Heck, even Wrath himself, the Ultimate Eye which is able to see everything, said that Greed has the impenetrable Ultimate Shield. Impenetrable means "impossible to break through".
And we did see Pride attack Greed's Ultimate Shield. He went for Greed's chin and Greed blocked it. That is all the proof you need.