two tasks cannot possibly be in the attentional focus at the same time.
one will inevitably end up being the focus, and the other - or others- more like irrelevant noise, something to be filtered out. or worse still, none will have the focus and all will be, although slightly clearer, noise, but degrees of noise all the same.

위 문장에서두번째 문장 ~ and the other 뒤에 동사 will end up being이 생략된건가요?
그리고 마지막 문장에서 although slightly clearer (than the noise to be filtered out) 걸러진 소음보다 모든 임무가 조금더 분명하긴하지만 이라고 해석되는데 내포된 의미가 정확히 무엇인지 ㅠ