From Guild Wars Wiki
Slashing Dmg: 15-22 (Requires 9 Swordsmanship)
Energy regeneration -1
Value: 220 gold
— in-game description
Zealous strength is an unofficial term for the inherent modifier that boosts damage by 14...15% at the expense of one pip of energy degeneration. It can only be found on weapons that drop in Prophecies or Factions.