The function of CYP4Z1 (cytochrome P450 family 4 subfamily Z member 1, ENSG00000186160) is as follows. A cytochrome P450 monooxygenase that catalyzes the in-chain oxidation of fatty acids (PubMed:19090726, PubMed:29018033). Catalyzes the hydroxylation of carbon-hydrogen bonds. Hydroxylates lauric and myristic acids predominantly at the omega-4 and omega-2 positions, respectively (PubMed:19090726, PubMed:29018033). Catalyzes the epoxidation of double bonds of polyunsaturated fatty acids (PUFA). Displays an absolute stereoselectivity in the epoxidation of arachidonic acid producing the 14(S),15(R)-epoxyeicosatrienoic acid (EET) enantiomer (PubMed:29018033). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH-ferrihemoprotein reductase) (PubMed:19090726, PubMed:29018033). {ECO:0000269|PubMed:19090726, ECO:0000269|PubMed:29018033}.