"When your capital is dealt dmg, deal 2 dmg to target unit in any corresponding zone." or something like that. Corresponding to the zone of mine which recieved dmg, or corresponding to the zone that contains my Longbow attachment? I'm trying to figure out if this is a worthwhile inclusion in a dwarf/wood elf deck that I want to build for an upcoming multiplayer game.

Corresponding zone on a card always means "corresponding zone to wherever this card is located".