User blog comment:Water Dragon Slayer/DREAM BATTLE CHRONICLES: FOURTH MATCH!/@comment-1393830-20130806042617/@comment-4829046-20130806090559

And I take those into consideration. Without his heart supplying him and healing him, Zero's killer techniques would be super effective. Hades will be able to overpower Zero but if Zero gets a good hit in, then its all over. Think about it, In the first few seconds of the Hades battle, he was completely owned by Team Natsu that had lost connection to the Island's full power and were extremely lacking in stamina and extremely injured as well. The only reason he was unscathed was because of his heart and I refuse to believe otherwise until Mashima himself states it. Cause lets face it, its an established fact that Old body < Young body.

Its a different story however if Hades uses long range Ametarasu from afar and defensive Ametarasu to block Zero's attacks. Either way I don't think Hades would be able to one-shot Zero. Let's not forget that even Zero's body wasn't at its peak. As Brain, the body was wrecked and I doubt it getting possessed by Zero completely healed it.