Exceptionally disturbing, with an undertone of horror and dread that you cannot quite pinpoint. At every moment, this film indeed does draw your Zone of Interest away from who would typically be considered the main characters, to the background. Sometimes it is a background visual of the fence of Auschwitz, or a sound eminating from over that fence. But often it is so much more miniscule, items and actions that would usually be ignored - lipstick, for instance.
The creators have done a truly moving job explaining the gut-punch feeling and disgust of the time period without being actually visually violent. Instead, they let your mind wander, which I find to be potentially more emotionally challenging.