What is there to say about the gameplay of zombicide? Well, first of all, it's scenario based. Which means that the map-tiles you get in the box are all arranged according to different scenarios with different objectives on them. It's a bit like Betrayal at House on the Hill in that sense except with all the tiles pre-arranged.
You distribute survivors among the players and you put them all in the starting zone. This marks one of the few problems I have with zombicide. When you only have 1 player, you use all 6 survivors. When you have 2 players, you each use 3 survivors and when you have 3 players, you use 2 survivors each. But once it hits 4-5 players, you only use 1 survivor each. This means the game gets harder for 4-5 people simply because you have less actions overall per round and less hp to spread around. Sadly, most of my gaming groups tend to consist of 4-5 people.
So each survivor gets a turn during the rounds which they can use to find critical mission items or just walk around exploring places or beating zombies. Once that round is done, zombies move and spawn. One of the things I like Zombicide is the fact that as you get deadlier in the game by earning experience points for your survivor, the zombie spawns every turn get deadlier.
When you're still at the newb level, the spawns are fairly tame, consisting of maybe 1 or 2 random zombies. However, when you hit the heroic level, then the spawns start consisting of more zombies and sometimes even deadlier zombies known as fatties or abominations. Plus, everytime you open a new house, zombies spawn in it as well, representing the zombies that have remained hiding.
However, the problem is that killing zombies will cause your experience level to increase rapidly, which makes even deadlier zombies spawn. So if your entire group isn't evenly levelled up, it can result in quite a few members dying. However, you can't just leave the zombies alone either, because if they reach you, they will automatically hit you. And once a survivor gets wounded 2 times, they're gone.
But if you manage to survive long enough, you'll eventually become overpowered enough that zombies will mean very little to you. Except for the abomination. That thing's just screwed up. In my very first game, we had 2 survivors with chainsaws and 1 character dual-wielding SMGs. We pretty much obliterated whatever zombies we came across before fulfilling our objectives and running away.
In the end, I'd say zombicide is a fun party game which is really easy to get into and requires very little explaining. It's one of those games you can bring out to non-board game playing friends (those heathens!) and even they will be able to grasp it quickly.