Catalyzes the NADP-dependent oxidation of 3,4-dehydroadipyl-CoA semialdehyde to form cis-3,4-dehydroadipyl-CoA. (3Z)-6-oxohex-3-enoyl-CoA + H2O + NADP(+) = cis-3,4-dehydroadipyl-CoA + 2 H(+) + NADPH Optimum pH is 7.2. Homodimer. By benzoate. Belongs to the aldehyde dehydrogenase family.