Marvel Zombies: Dead Days answered some questions, but created more.
Why didn't Franklin reality-warp things?
How did a needle prick Thing?
How did Colossus get infected in his metal form?
Why did Thor, Dr. Strange, and the others just kinda stand there and let the zombie-FF infect them? Thor beat on the zombie-Thunderbolts and zombie-Abomination, but the zombie-FF are too much for him AND Colossus, Storm, Nightcrawler, Dr. Strange, and whomever else? I've had a feeling for a while that everyone in the zombie-verse are chumps... I think this book confirmed it.
I wonder who Magneto talked to? Are we going to find out in MZ vs. AoD?
How did zombie-Spider-Man magically appear behind DareDevil?
Black Cat and Iron Fist were on the Helicarrier, but in MZ vs. AoD they showed zombie-Black Cat infecting Iron Fist... which took place before the Helicarrier scene.
I think this book also confirms my theory that the zombie cameos are non-canon.
Why didn't Nick Fury just let Black Bolt go do to the city by himself and yell "No More Zombies"?
In the group spread, I saw Machine-Man in his old look... but in Marvel Zombies vs. Army of Darkness he was in his new look with Next Wave.
How did Reed figure that zombies use less energy? They're constantly hungry. And how did he figure that they're immortal? I would had loved to argue with Reed on how zombification is the next step in evolution. Your heart has stopped, your organs no longer function, you can't reproduce, you can't heal, you're decaying, and you become irrational. Sounds to me like an evolutionary stand-still that severely shortens your life-span and strips you of the ability to adapt.