Abba and Imma direct Zeir Anpin through his Mental Powers; the Keter derives from Arich Anpin.
Z"A's structural anatomy: body / Mochin / Keter. Mental Powers come from Abba and Imma; Keter comes from A"A. CHaDaR runs through Z"A because the cycle of six thousand years requires it.
Op. 116 specifies Z"A's interior anatomy and the structural-cosmogonic reason for it. The chapter is the operational anchor of the entire Z"N unit.
Z"A's upper-internal structure: body at the lower-anatomical level; Mochin (Mental Powers — Chochmah, Binah, Daat) at the middle; Keter at the apex. Two upper-source channels: the Mochin channel (from Abba and Imma) and the Keter channel (from A"A). The two channels merge in Z"A's interior.
CHaDaR runs through Z"A from body up through Mochin. This is the operational form of the cosmic government at the deed-relevant level. The three-column structure — Chesed, Din, Rachamim — operates at every anatomical level of Z"A, with the upper Mental Powers articulating each column as a Mental-Power-of-CHaDaR.
The striking claim: CHaDaR runs through Z"A because this is what is required for the entire cycle of six thousand years, the period of service. The structural form is what the cycle's purpose demands. Without CHaDaR, the cycle's deed-dependent operating mode would have no operational matrix; with it, human service has the cosmic-anatomical context in which to be performed.
Op. 124 (Daat as the bridging Mochin) operationalises the Mental-Powers-of-CHaDaR doctrine. Op. 138 (the closing operational mechanism) operates within Op. 116's framework.