better to take taxi or Auto as metro will be quite circuitous. NZM to Gail Noida is around 10km. NZM -- ashram -- DND Flyway -- Gail, sector 1, Noida.
if you want to take Metro then nearest Metro Railway station is IndraPrastha Metro station(5km from NZM) from there you have to take metro for sector 15, Noida. from Sector 15 to Gail Noida is around 1km.