One criticism so far, I don't really see what the point of the guys you have to do multiple lines on, wouldn't it make more sense to just have more guys come on?
Go to hero > upgrades, repeatedly select attack, then do mission 5 to collect as much leather as possible, repeatedly craft worn belts, then go equipment under the hero tab, select the belt, and then get a screenshot once you've crafted five of them so you can prove you've crafted five items. Also you do more damage at close range, so try to stay close to one individual zombie while you try and pick it off, while remaining as far from the other zombies until you're able to take it down.
I'm glad you liked the game! I appreciate it.