Okay, first I have to say that the concept here is decent, but I absolutely hate the main map. It looks like just about zero effort was put into it. If anything, the chevron should indicate how much experience your units have, not what they are. Your characters hold the handgun wrong when marching. They should either go to low read (same as a shooting stance, but aimed at the ground) or high ready (same grip, arms bent at the elbow, gun pointed up); the palm under the magazine thing you're doing is not a recognized shooting stance. Your assault rifles look like utter crap. It resembles an M1 Garand or M14 with an AK magazine. You should have them using the M16 or M4. Also, the carbine as a power weapon is just plain weird. Carbines fire the same caliber bullet as an assault rifle; all that changes is a carbine has a shorter barrel. Thus, the carbine should be the mid range gun, while the AR is the superior model. You might also want to think about including more units and guns. I.E., replace the pistol unit with a CQC squad armed with handguns and later shotguns, a rifleman class armed with carbines and then assault rifles, and a marksman class armed with battle rifles (like the M14 or FAL) which can be upgraded to a sniper rifle. I would also delete the knives entirely; have your guys always switch to handguns instead; which would you rather have against zombies: a GUN, with range, or a dinky little knife that puts you within biting distance?
There were other issues, too, such as my units kept routing for no decernable reason. I can understand five guys armed with handguns running from twenty zombies, but that same mob was also putting my mechanized infantry to flight. The combat screen as a whole looked the best, although it too had issues. At one point one of my infantry men got stuck in his knife animation, with his arm fully extended behind him, and somewhat more amusingly, one of my rifleman decided to keep advancing while the rest of his squad ran the other way, only turning to run less than two feet from the zombies.
Also, instead of a powerpoint, you need an actual tutorial level. Maybe keep it separate from the main game (so people who've played it before can skip it), but so I don't have to sit and click through 30+ slides like it's suddenly biology class again.
Overall, this game has promise, but it needs work, and that's my honest opinion.