The proposition has two parts: Part 1: Through the Mental Powers… This explains what Zeir Anpin’s Mental Powers are. Part 2: According to the strength… The body is governed entirely by the Mental Powers.
Part 1: Through the Mental Powers of Zeir Anpin … The main essence of Zeir Anpin consists of the Six Directions – Chessed, Gevurah, Tiferet, Netzach, Hod and Yesod. This is because the function of Zeir Anpin is to serve as the root of the creations of this world, to sustain and govern them, and all this is only through the Six Directions. However, the Mental Powers exist in Zeir Anpin by virtue of the way Abba and Imma are grafted into him, as the proposition goes on to state.