In the fight over whether to rezone Prospect Lefferts Gardens in Brooklyn, a few industrially zoned blocks have become major sticking points. Activists have argued that a few highway-like blocks along Empire Boulevard, at the northwestern edge of the neighborhood, would produce high-rise development and gentrification if they were rezoned to allow new apartments. But there are two more industrial blocks at the southern end of the hood, on Parkside Avenue between Rogers and New York avenues, and now, a new building may replace an old warehouse there at 640 Parkside Avenue, between Rogers and Nostrand avenues.