This gets tricky fast, depending on the brain power your group puts into their games.
"Zero-Zones" are MCT's biggest strength and weakness. Strength because they have a reputation for leaving zero survivors. Weakness because they are never, EVER applied right

A 0zone is never going to be somewhere that someone could "accidentally" fall into. And nor are they lethal beyond their borders.
A 0zone is never going to be around a MCT shopping mall, or public office building in the middle of downtown... BUT it would be (possibly) around there private research building in a suburb.
The First line of defense is almost ALWAYS A... Sign. A simple, plain sign. Hung in both AR and meat-space that usually has big red letters that says: PRIVATE PROPERTY, NO TRESSPANSING. LEATHAL ENFORCEMENT BEYOND THIS WALL. <First rule of ET: All borders must be clearly marked and delineated.> And is usually hung from a 20foot high concrete wall.
Why Concrete? and why 20 feet?
Simple. The wall is the second barrier to entry, and also exit. It also stops MCTs "security measures" from leaving their property and causing a diplomatic incident. <No one cares that the US carries out ballistic missile tests on US soil. BUT, they get mighty pissed when those ballistic missile start falling on neighbours' soil

Same thing for objects travelling at high speeds... like lead from Corp property...>
From there, the third challenge is the terrain on the other side of the fence. Landscaped with hedges, reflecting pools, and patio furniture; Or just an open field of grass, this is the next problem for the Runners. Every bush is a hiding spot for a Sensor, turret, monowire, or drone. Every patch of open space a spot for a land mine... Expect over lapping sensors covering everything from movement, to pressure, to heat. Once one of those sensors is triggered, one can expect hidden turrets to provide overlapping fields of fire leaving no angle nor alcove uncovered. Drones will be used to provide both areal fire and target tracking. If employed, biological countermeasures will be deployed. (Critters, Paracritters, meta-human guards). Lastly the facility itself will be alerted and placed on lockdown.
Once the distance from the wall to the building has been covered, the fourth challenge is now entrance TO the building. Expected a Hardened structure (for at least the first 3 floors. to resist damage from outside defenses), covered in sensors for pressure and harmonics (certain noises.. like glass cutting, or concrete fracturing). The outside of the building is usually also lighted, to cut down on hidden spots a person can hide. All windows and doors will be polarized and reinforced. Rooftops, garage entrance ways, and doors will have sensor webs and countermeasures.
Finally, inside the building will be the last challenge. Expect funnelled hallways to choke/checkpoints, Security Doors and gates along said pathways and into the various departments and wings. Patrols by both drones, biologics (critters, paracritters) and guards will be overlapping and randomized.
For magical security, you can count on wards to be placed in an overlapping fashion to increase the chances of detections. Such as a ward covering the outside of the building, then wards at every choke point. (security stations, elevators, doors, gates) Essentially anyplace there is a physical barrier, there is an astral one as well. Paracritters and spirits will be on patrol in overlapped routes for maximum coverage.
The building will also contain a "Rapid Response" security team in addition to anything that is normally assigned to a standard facility, as well as possibly elite units if the assets warrant it.
Defeating a Zero Zone is something that takes extreme planning, detailed tasking, and a metric crap-tonne of luck.