Polymer interphase on Zn anodes obviates dendrite growth and significant side reactions including corrosion and hydrogen evolution in aqueous zinc ion batteries (AZIBs), however has drawbacks of slow kinetics and large overpotential for Zn plating/stripping that prevent practical application especially under high-rate conditions. Here, a multifunctional polymer interphase with fast kineticsis reported, using poly(phenazine-alt-pyromellitic anhydride) (PPPA) as an electrolyte additive. PPPA, with linear π-conjugated structure and enriched polar pyridine (conjugated cyclic -C=N-) and carbonyl (C=O) groups, preferentially adsorbs on the Zn anode to form a stable solid-electrolyte interphase (SEI) layer in situ. The PPPA SEI is efficient to block direct contact between water molecules and Zn anode, and regulate the interfacial solvation structure and Zn depostion. Importantly, the expanding π-conjugated structure of PPPA is shown to provide abundant 2D open channels for rapid Zn