Is it for a western style comic, manga or manwha format ?
I can only speak for western style as it is my field, but if that's the case, the script should be divided by pages. If you want to shock the reader with a sudden reveal, make sure the reveal in question is the first thing you see when they "turn" the page or that it covers the whole page (think Junji Ito, he does it all the time).
The visuals are extremely important and should be planned in advance. Which case is going to be bigger, larger, what position will they occupy in the page ? Make a template for each page and keep the rhythm in mind. The larger the case, the longer the scene.
Right now with the base script, those aspects are completely missing, so it's impossible to tell how well it would read.
In any case, the concept is interesting, it's a nice twist on traditional zombie stories. But be careful because these are a dime a dozen, so you have to make sure to have striking visuals to make it stand out.
Anyway, good luck with your project ! Feel free to post on our wall if or when you end up uploading an episode. I'd be happy to give it a read.
Dorian