Zaken's Earring of Immortality "Its effects are MP+37, resistance to Bleed +30%, Bleed attack rate +30%, heal amount +15%, vampiric rage effect, resistance to Shock/Mental attacks +30%, Shock/Mental attack rate +30%, and Darkness attribute defense +15. Only one effect is applied even when the same two earrings are worn. If it is equipped together with a standard Zaken's Earring, only the effect of Zaken's Earring of Immortality will be applied."
It is written that the bonus will not cumulate with a standart Zaken Earring, so I think MYSTERica is right :)