Iterative Twisted Approximation (ITROX), proposed in 2012 by Soltanalian et al., is an interesting algorithm for designing sequences with desired correlation properties. However, when aperiodic correlation of unimodular complementary and Zcomplementary sets (ZCSs) are considered, the correlation magnitudes of the resultant sequence sets of the ITROX algorithm, are not as good as desired. In this work, we have proposed a new modified ITROX algorithm, which can design unimodular ZCSs. Also the correlation levels of the resultant unimodular complementary sequence sets are better as compared to the previous ITROX.