Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
When this card is Normal Summoned: You can target 1 Zombie monster with 0 DEF in your GY; add it to your hand. Gains 300 ATK if you control another Zombie monster(s).
--冥界騎士トリスタン
--Tristan, Knight of the Underworld
local s,id=GetID()
function s.initial_effect(c)
	--tohand
	local e1=Effect.CreateEffect(c)
	e1:SetCategory(CATEGORY_TOHAND)
	e1:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_O)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetCode(EVENT_SUMMON_SUCCESS)
	e1:SetTarget(s.thtg)
	e1:SetOperation(s.thop)
	c:RegisterEffect(e1)
	--atk
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_SINGLE)
	e2:SetProperty(EFFECT_FLAG_SINGLE_RANGE)
	e2:SetRange(LOCATION_MZONE)
	e2:SetCode(EFFECT_UPDATE_ATTACK)
	e2:SetCondition(s.atkcon)
	e2:SetValue(300)
	c:RegisterEffect(e2)
end
function s.thfilter(c)
	return c:IsDefenseBelow(0) and c:IsRace(RACE_ZOMBIE) and c:IsAbleToHand()
end
function s.thtg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_GRAVE) and chkc:IsControler(tp) and s.thfilter(chkc) end
	if chk==0 then return Duel.IsExistingTarget(s.thfilter,tp,LOCATION_GRAVE,0,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_ATOHAND)
	local g=Duel.SelectTarget(tp,s.thfilter,tp,LOCATION_GRAVE,0,1,1,nil)
	Duel.SetOperationInfo(0,CATEGORY_TOHAND,g,1,0,0)
end
function s.thop(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) then
		Duel.SendtoHand(tc,nil,REASON_EFFECT)
	end
end
function s.atkcon(e)
	return Duel.IsExistingMatchingCard(aux.FaceupFilter(Card.IsRace,RACE_ZOMBIE),e:GetHandlerPlayer(),LOCATION_MZONE,0,1,e:GetHandler())
end