US-P18.021ab ।US-P18.021cd ॥
In plain words
That superimposition is what "not this, not this" cancels — the śruti takes it as already in place, and strikes it out. And no command to superimpose again, from any source at all, holds up.
Close to the Sanskrit
That superimposition, as something already obtained, is negated by 'not thus, not thus'; any injunction of superimposition over again, from any source whatever, is not tenable.