I had to look up what "Kaizo" meant... from a Japanese term referring to a (usually absurdly difficult) hack/mod popularized by a super mario world hack released sometime before 2013... often "trial and error" based custom levels for popular games. You learn something new every day!
I'm not sure about replaying it exactly as stated, but that's a judgement call on Zargon's part. Relying upon memorization as a way to defeat a purposely broken quest designed to be challenging by random death seems a little off, but whatever (why are we even playing it then? maybe we're playtesting a friend's quest?).
I guess my solution to what I consider brokenly-difficult official quests (like EQP/BQP) is to have the heroes slowly earn bonuses and increased abilities in earlier quests so they are strong enough to weather the storm by then, to a reasonable degree while still experiencing challenge to their skills. If they all die, I'm still changing things around a bit on the replay. It doesn't say Zargon needs to make the quest harder the second time, the point is to make it not a case of being easier due to memorization (similar to if half your group just completed the quest last week and you're doing it again with a a new person, would you leave it exactly the same? maybe if the pure newbie, like a little kid...).
I hear you on giving more charity to the "official" quests from back in the day than to fan-created ones. But even still, I think as Zargon I'd try to fix what was broken beforehand, than trying to feel like I'm cheating just to be able to cross it off the list. There are so many quests out there, surely there is a better option?
Agree about setting the expectations with the players ahead of time though! Especially now with so many different, possibly conflicting expectations of how it's supposed to go.