Zapper is a special feature, entirely unrelated to cosmetic filtering. When you zap an element, the element is removed from the DOM, and the zapper code will also look at the DOM to find out if any of the parent elements are scroll-locked, and if so will defuse it with an inline style using `!important`.[1]
As for cosmetic filtering, it's is the hiding of elements using `display: none !important`, so `!important` is also key to ensure page styles are overridden.[2]