Volume VI (E): The Enthalpy Bank – The Zhangyu Standard, the Four-Layer Asset Architecture, and the 2.0 ZY Bankruptcy Firewall

Volumes I–V of the N.E.A. series have constructed the complete physical and biological account of reality. With the currency defined and the hardware audited, this volume constructs the Enthalpy Bank—the four-layer accounting ledger in which all physical, biological, civilizational, and cognitive assets are denominated in Zhangyu (ZY). We provide rigorous ZY-denominated proofs of the dimensional uniqueness theorem (d=3 is the only solvent integer dimension under finite bandwidth), the quantitative elimination of the Luxury Solids as physical force carriers, and the 2.0 ZY Bankruptcy Firewall as the absolute topological liquidation threshold. We establish the Shared Edge Dividend Lemma, which resolves the apparent degree ambiguity in the C8 tiling scaffold, and the Locking Premium Theorem, which explains the effective logical degree of fully locked K4 simplexes under SU(3) confinement. The four layers are: Layer I (Physical Infrastructure, H=1.3333 ZY), Layer II (Biological Efficiency, H≈1.25 ZY), Layer III (Civilizational Credit, H≈1.15 ZY, illustrative heuristic benchmarks), and Layer IV (Observer Sovereignty, H≈1.0117 ZY, heuristic). The Protocol Vacuum Zone between 2.0 ZY and 3.0 ZY is formally defined as a conceptual regime of degraded operation. The Law of Topological Diminishing Returns and the ΔH≤0 evolutionary constraint provide the theoretical foundation for relaxation oscillator dynamics governing civilizational cycles. The tiling origins of value are established: the Zhangyu is the universal unit of "failed space"—the rent paid when a geometric carrier cannot tile and is forced to exist as localized matter rather than diluted background. All derivations inherit constants exclusively from the GTUOC sequence, ensuring a settlement process free of ad‑hoc cancellation mechanisms, except for the Layer III civilizational benchmarks which are explicitly marked as empirical calibrations. Five quantitative figures provide numerical validation across physical, biological, and civilizational scales.