Is anyone fluent enough with the POI editor in 7d2d to be able to ckeck that trigger out?
U.S. Army Post #7 is base_military_01. This isn't the POI I thought y'all were talking about. I think one has been revised since I last played it. I don't remember it being Tier 5.
I think you're talking about the bottom floor. I think I see 4 zombies volumes all linked as "Group 3". I don't see a trigger but three of those volumes are marked as "Active." I don't recall if I can stealth an active volume if I don't enter it. If so, then you must not enter that restroom or the bedrooms until you clear them. BUT, that won't clear the minscripts, so you're going to activate something eventually and eat at least half of the nasty ambush.
Hallway/Dining has 5 wandering zombies. This is probably what you clear before you enter the restroom or the Bedrooms.
Restroom/Showers has a minscript: Spawn 10 soldiers, wait until there's 4 left, then spawn 10 more.
Bedroom to West (officers quarters?) has a minscript: Spawn 5 soldiers; wait until there's 2 left, then spawn 5 more.
Bedroom to East (barracks?) has a minscript: Spawn 5 soldiers; wait until there's 2 left, then spawn 5 more.
I suspect you stealth the 5 wanderers in the Dining room then activate the other 3 volumes when you enter any of them to eat 20 zombies at once, with 20 more in reinforcements as the first wave is thinned out. No matter which of the 3 volumes you entered, the zombies from the other 2 will be behind you.
Your best bet is either activate the East bedroom or the bathroom then flee back to the elevator. The elevator door has 10,000 hit points, so close that. You might be able to recover stealth hiding in there, but that's a lot of zombies to beat down that door.
You would have to prepare the elevator to be an exit because you can't reach the ladder to get back up if you don't, plus the grate on the wall of the elevator might block jumps. If you can jump to the top of the elevator that would be your next chance to regain stealth, but you may still be pretty close to active zombies.
Your next fallback would be the top of the elevator shaft but you'll be on a ladder so no stealth as you climb. You'll probably be unable to reach the door unless you put some blocks down. Then, finally, up there on the roof of the building I'll bet you could recover stealth.
That's just from looking at it via the POI Editor. I have not played it... at least not this version.