Almost unplayable.
This game has great graphics, a great sound track, and a great concept, only the control scheme is just so awful I can't give it more than a 3/5. Normally I would give more stars from the effort, but since it's obvious that you're a good enough designer to know better, I'm giving you my full wrath and docking two full points for this screwup.
The single largest issue with this game is that soldiers act on their own WAY too much. Automatically reloading, automatically attacking, automatically looting. It was unbearably obnoxious and it made it physically hurt to play the game due to the fact that playing this game was an almost entirely passive experience.
I get that automatically reloading is supposed to be a convenient feature, but I would rather have the character flash orange when they're out of bullets and red when they're low on health... Also making interactive objects blink when the grid is set to appear would have been nice. This all snowballs into its own little problem of its own: As a game designer, it's important to let your audience know exactly what's going on in a game. Blind spots, whether in an action, adventure, driving, or strategy game (or all the other genres I didn't mention) are extremely annoying and can quickly make a great game unplayable.
Also let me point out how ludicrous it is to reload from a supply box one bullet at a time. If you wanted to make the game harder, you should have made the zombies stronger. Certain actions like that, or like the stat system which would have normally given the game more polish instead felt superficial, unrealistic, and annoying. You're severely lacking in aesthetics here!
That being said, I think the whole tile-based real-time strategy concept is awesome, and I think it's a great way to stimulate to make quick judgments while also being an extremely realistic way to think of battle tactics. Part of the reason this game pissed me off so much was because I genuinely wanted to enjoy and get to like this game.