Zid is a common Hindi/ Urdu word which means insistence, persistence, or doggedness.
It can be used as a noun, as well as a verb, the latter as 'zid karna', that would mean to be stubborn, to be obstinate, to decide something and just not budge from that.
I would like to add here that zid is mostly considered a negative thing, especially since every child in Hindi/Urdu speaking regions is asked not to do 'zid', or not to be 'ziddi'. Ziddi is someone who does zid, someone who shows stubbornness, or is being stubborn.