I've had extremely good luck with LeverEvolution in .30-30. I can't say anything about the Zombie Max, but then I've never gone Zombie hunting - because, you know, zombies are imaginary.
Even if it somehow failed to expand it's still going to be a bullet, and should still do the job if it's in the right spot, so I'm going to have to agree with the consensus that you probably missed - groups on paper are always better than you can expect in the field.
The same thing actually happened to one of my hunting buddies this year - deer jumped, blood and hair on the brush behind him, but off it ran. Only difference is, we spent the rest of the day tracking it. IMHO that's the difference between "hunting" and "shooting at animals". But, the perception's probably different hunting up north where you might only see a couple deer in a day.
si vis pacem para bellum