Is it permissible to marry the daughter of the maternal aunt (S), who is the daughter of the daughter of the wife of the grandfather (N) through the suckling of the grandmother's sister (Z)?

If you were breastfed by your grandmother in a manner that is Islamically recognized, then it is not permissible for you to marry your maternal aunt's daughter, because you would be her maternal uncle through suckling. Marrying her is forbidden due to the Prophet's saying: "Suckling prohibits what lineage prohibits."