Book VI of the Konika is essentially devoted to the question of the identity and similarity of two conic sections, or two parts of conic sections. In Book VII Apollonius deals with the various relationships between the lengths of diameters and conjugate diameters. The results are applied to the exposition of a number of problems, as well as to some problems which Apollonius indicates will be demonstrated and solved in Book VIII, which was lost in Antiquity. Books VI and VII have only survived in an Arabic translation, and are presented here in a critical edition, together with a faithful translation and a historical-mathematical commentary.