Either you use GreeN!X's system and use units instead of destructibles. You can then choose to either use an armor system, or use unit-specifications to deal more damage (Undead, Tauren, Mechanical, Ancient etc).
If you still want to use destrictubles, you have the fun way of using triggers for the damage, and then use If then else cases:
This happens when a destruct is either attacked or an ability is used on them, it's up to you.
If Destruct-Type == Summer Tree Wall or Winter Tree Wall or Village Tree Wall..
//It's a tree! See what damage we shall deal
if (ItemCarried by hero of type Axe != no item)
Deal huge damage
else if (ItemCarried by hero of type Shovel!= no item)
Deal medium Damage
else if (ItemCarried by hero of type Pickaxe!= no item)
Deal medium damage
If Destruct-Type == Rock Small or Rock Large.
//It's a rock! See what damage we shall deal
if (ItemCarried by hero of type Axe != no item)
Deal low damage
else if (ItemCarried by hero of type Shovel!= no item)
Deal low Damage
else if (ItemCarried by hero of type Pickaxe!= no item)
Deal Huge damage
Psuedo code ftw!