Complex sentence: It lies almost due south of the larger Daedalus crater, and across the longitude that is diametrically opposed to the Earth-zenith: that is, it is nearly opposite the point on the lunar surface that is the most directly below the Earth.
Split into simpler sentences: It lies almost due south of the larger Daedalus crater, and across the longitude that is diametrically opposed to the Earth-zenith. That is, it is nearly opposite the point on the lunar surface that is the most directly below the Earth.