This is the 9768th most frequent Polish word.
zgierskiej
"Zgierskiej" is the genitive or locative form of "Zgierska," which refers to something related to the city of Zgierz in Poland.
In this sentence, 'zgierskiej' is an adjective derived from 'Zgierz', a town in Poland, and is used to describe a noun ('ulicy' - street) as belonging to or related to Zgierz.
Nie wiem, jak dotrzeć do zgierskiej ulicy.
I don't know how to get to the Zgierska street.
Here, 'zgierskiej' modifies 'imprezie' (event), indicating the event is related to the town of Zgierz.
Spotkaliśmy się na zgierskiej imprezie planowanej przez mieszkańców.
We met at the Zgierz event planned by the residents.
In this context, 'zgierskiej' describes 'strefie przemysłowej' (industrial zone), specifying its location in Zgierz.