✓ Both are tactical first-person shooters — sharing shooter, first-person shooting and third-person shooting
≠ Its own twist: deep simulation, stealth mechanics and ranged combat, while skipping adventure storytelling
The 2005 original that started the series: a lone OSS sniper in the ruins of Berlin, built around bullet drop, wind and breath control at a time when few shooters modelled any of it. The ballistics still hold up. Everything around them does not — movement is famously slippery and frame-rate dependent, the controls are unmapped and awkward, and the tutorials interrupt constantly.
Where it drifts furthest from Zombie Army Trilogy: setting.
On reception: its Steam reviews are mostly positive, against very positive for Zombie Army Trilogy.
It predates Zombie Army Trilogy by 10 years, with what that implies technically.