If more than one equipped creature you control attacks, Nazahn's last ability triggers once for each of those creatures. It doesn't trigger additional times for additional Equipment attached to an attacking creature.

Nazahn's last ability can target a creature controlled only by the defending player who is being attacked by the attacking creature that caused the ability to trigger. For example, if an unequipped Nazahn is attacking player A and an equipped creature is attacking player B, Nazahn's ability can target only a creature player B controls.

If a creature is attacking a planeswalker, its controller is that creature's defending player.