Unfortunately, from what I have heard from stories before my time, the down-zoning of commercial streets in Chicago neighborhoods is not a new thing.
As an architect who lives and works out of Pilsen, I do work for many longtime Mexican business and building owners across the southwest side. From some of them, I have heard of cases (35th St in McKinley Park for example) where they feel this was done in a effort to stop Latino businesses from opening as the neighborhood demographics shifted. The Aldermen who did these shenanigans are gone, but these commercial corridors remain relatively vacant, especially compared to other vibrant streets in these neighborhoods where zoning was unaffected or subsequently restored.
Hopefully, the Aldermen who propose down-zoning today have better intentions, but I think that these measures, if enacted, would fail similarly and lead to slow attrition of the businesses in these corridors. But then again, if they really do want to turn them into single family districts, maybe that's the point.
Here's another example from the reader from 1998.