Very good first attempt
Attention to detail being that you gave certain zombie types random parts (or so it sounds, I'm not sure I believe it worked). No guns were terribly powerful until the barret, which made the game WAY to easy. The only difficult time I had at all was around days 3-5ish, before you get the shotgun, it can be a bit of a pain, since nothing is very powerful.
Personally I think the game could use some enhancment of difficulty, a little more creativity (its hard with zombie games to be creative, you did fine, but it's still A. a zombie game, B. a bit repetative by the end).
To "starlancer" and "envee", you're a couple of funny to read newbs that I'm surprised got so upset just cause they can't touch a few levels of a relativly easy flash game, get over it, and stop blaming the author for you sucking lol...
Back to topic... I would say that next you should go for a completly different style of game, and use your imagination to add inovative features. Dont repeat this or things remotely close, because a lot of fans will probably say "its just like the first one" if you follow me. You have good innovation, use it to full effect by raising the bar on another genre.