In [9], the concept of fuzzy sets is applied to the theory of Ζ-ideals in a BCI-semigroup (it was renamed as an IS-algebra for the convenience of study), and a characterization of fuzzy Ζ-ideals by their level Ζ-ideals was discussed. In this paper, we study further properties of fuzzy Ζ-ideals. We prove that the homomorphic image and preimage of a fuzzy Ζ-ideal are also fuzzy Ζ-ideals.