This paper introduces a new system of extended generalized nonlinear mixed quasi-variational inclusions involving -maximal -relaxed -accretive (so called -accretive (Lan et al. (2006) [37])) mappings in -uniformly smooth Banach spaces. By using the resolvent operator technique for -maximal -relaxed -accretive mappings due to Lan et al., we establish the existence and uniqueness of solution for this system of extended generalized nonlinear mixed quasi-variational inclusions and construct a new perturbed -step iterative algorithm with mixed errors for solving the mentioned system. We also prove the convergence of the sequences generated by our algorithms in -uniformly smooth Banach spaces. The results presented in this paper extend and improve some known results in the literature.