Munchkin Zombie | Plague Card | Death Breath
 

Plague zombie: "death breath: against monsters of level 11 or higher, you can discard up to 3 cards from your hand for +2 each to your side"

Can I discard carrying or used items to get +2?

Card said: "cards from your hand".

But rules say: "Some Mojo abilities are powered by discards.
You may discard any card, in play or in your hand, to
power a special ability".

Re: Munchkin Zombie | Plague Card | Death Breath
 

Specific rules on cards take precedence over the general rules. In this case, you must discard from your hand because the Plague Zombie card says so.