I guess the next question then is: untouched by what? If you make the zone no-reset, then the game itself won't touch the zone ever and you'll need to set a trigger to make the zone reset or appear to reset.
My tarot zone sets up a small area just for one player and if you look at the triggers, they do all sorts of weird stuff to try to make sure nobody interferes but also that nobody can 'hog' the set of rooms. There's also a trigger to clear the rooms when no longer needed.
I have a maze zone in progress on the buildport which triggers a layout and resets the zone when a new maze is needed. There's more information on that
here
. I haven't worked on it lately because it's mostly slog work needed now so I'm not sure what sort of shape it's in.
If you're thinking that you want the player to be able to go in and out of the small section, how about making a 'key' item to allow that player access but nobody else can get in. Tarot has 3 private sections but it seems that you might want, say... 4 or 5 sections depending on how many treasure rooms and so on that you need. If you keep the 'keys' in one room, find obj will show if a key is missing and that section cannot be accessed by any other player. If all 'keys' are gone, nobody else can play the zone until an earlier player finishes and returns it.
I say 'key' because it should not actually BE a key-type but a treasure or trash in key form.
I'm not sure if this is what you're looking for but if not, please let me know. Now that my brain is on this, I could probably make another unfinished zone along those lines myself