I think
@loverdrive and
@pemerton both touched on the really core thing. In ZM there's no such thing as a point where a player describes an action which seems plausible fictionally and then the GM says "no, that fails" and the reason is some sort of thing they cooked up last week but never incorporated into shared fiction.
GMs can prep as much as they want, and introduce stuff from their notes, but it doesn't supercede anyone else's say at the table. Thus it's pretty unlikely that a GM is going to just dictate the story, not for long! Also the game has a say, and that also holds, no illusions, no fudging, etc. ZM narrative play is very open! If you want to bring on the Ghoul Palace, talk about it, ask questions, etc. You don't have to reveal every detail ahead but you should be serving up a meal the table wants.