There are 4 deadly threats in a zombie outbreak, and only of them is zombies. We have the zombies; that's the obvious one. Second threat is other hostile or desperate humans. If you don't account for other people who are potentially going to want to take your stuff or need to take your stuff, just not because they're bad people, just out of serious personal need, you're going to have real problems. The third threat is what I call The System. The System is any outside government agency or body that is going to try to exert its will on you.
At the first sign of zombies, you can believe there's going to be a bureaucrat somewhere who says, "I got to get a handle on this. I'm supposed to be in charge." What they're going to is they're going to draw a line around a quarantine zone. You may have the perfect Zombie Survival Plan, you may be all stocked up in your house and ready to go, but military trucks going to show up at your front door and they're going to escort you out. They're going to take you down to the Refuge Center and put you next to a guy who's wearing a long sleeve shirt and looks a little sick. It's going to turn out he's been bitten by a zombie, and you're all going to get eaten.
The fourth threat is yourself. It has been played out time and time again that in extreme survival situations, the person that survives is not the most prepared, is not the fittest, is not the strongest; it is the person that can keep their head screwed on straight. Your own ability to keep yourself calm in extreme situation is what's going to be the difference between life and death.
Any Zombie Survival Plan that doesn't account for all 4 of the deadly threats is essentially not worth the paper it's printed on. You may have the best Zombie Survival Plan that's focused solely on zombies, but chances are you're going to find yourself killed by one of the other 3 threats.