Armor Bonus and Weapon Bonus are weird, sometimes your Armor gives you Weapon Bonus and vice versa
Also remember this: if you item says "Deal x% damage" it means +(x-100)% damage
Example 1: Reaper Armor (Deal 200% damage to zombies) means +100% damage to zombies
Example 2: Axe of the Shredder (Deal +250% damage to zombies) is +250% damage to zombies, just like the description
The difference is the "+" symbol, remember that
Also, those items are good example of the first line, AotS gives you Armor Bonus for some reason