What finally worked:
setglobal
"41NateDestroySourceQuest","GLOBAL",4)
The game didn't recognize createcreature so I browsed Infinity Explorer and looked up some variables. I didn't get any experience, but it was better than combing the Ice Temple for hours.
I also couldn't get Zack to give me the belladonna. I had a similar problem with Oswald and the ship parts. Do those events run on timers?