Zeir Anpin and Nukva — root of the lower creations.
Z"A and Nukva are the immediate cause of the lower creations. The higher Partzufim are indirect causes operating through Z"N.
Op. 115 opens the Z"N General Principles unit (Op. 115–118) with the structural anchor. Z"A and Nukva are the operational endpoint of the chain Op. 114 traced. The lower creations — the world we know — receive cosmic governance immediately from Z"N; the higher Partzufim govern through Z"N rather than directly.
The distinction immediate cause vs indirect cause is structurally crucial. Immediate: Z"N is what acts on the lower creations directly. When the cosmic government produces an operational effect in our realm, Z"N is what produces it. Indirect: A"A, Abba and Imma, Atik Yomin — these contribute to the cosmic-operational reality, but they do so through Z"N. Their influence reaches the lower creations only via Z"N's mediation.
This is why the cycle's deed-dependent operating mode is Z"N-centric. Human service elicits cosmic response through Z"N (specifically, through Nukva-as-receiver-and-distributor). The closing chapters' Coupling-order doctrine operates at the Z"N level because this is the operational level at which the cosmic government meets actual creation.