head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Practiced Mastery
Patient ballistic aiming wrapped in plannable stealth positioning.

Execution · Practiced Mastery
A co-op horde shooter testing sniper aim and chokepoint planning against scripted waves.
Sniper Elite V2 leans Execution (Practiced Mastery); Zombie Army Trilogy leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Sniper Elite V2
Ballistics-compensated long shots demand steady precise aim
Zombie Army Trilogy
Long-range sniping and horde kiting demand steady aim
Sniper Elite V2 leans a little harder on reads, though the gap is small.
Sniper Elite V2
Enemy AI runs fixed alert routines
Zombie Army Trilogy
Undead waves follow predictable spawn scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Sniper Elite V2
Wind and patrol details vary slightly per attempt
Zombie Army Trilogy
Spawn timing varies a little between runs
Sniper Elite V2 leans a little harder on optimization, though the gap is small.
Sniper Elite V2
Positioning, sound masking and route planning are learnable
Zombie Army Trilogy
Choke points, trap placement and ammo economy reward planning
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.