Jinzo/Skill Drain Question

Ok so my friend activated the trap card Skill Drain. (Pay 1000 Life Points to Negate the activation of Effect Monsters) but then his Opponent played Jinzo, which as you guys prob know Negates all traps, so they argued about which is negated, then his opponent rage quit, so he wanted me to ask which is correct? is Jinzos effect negated, or is Skill Drain Negated ?

Yeah, I'm pretty sure Jinzo's effect would of been negated, considering I activated Skill drain the turn before he even summoned the card, but I just need to know for sure.

If Skill Drain is on the field 1st, then Jinzo's effect is negated when he is summoned.

If Jinzo is on the field 1st, then Skill Drain cannot be activated in the 1st place because Jinzo forbids either player from activating their trap cards.

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