My understanding is converting huge office buildings into apartments/condos isn't cost effective or even possible a lot of the time. So they could re-zone, but possibly need to demolish/rebuild.

Maybe this will spur innovation in building for buildings that can easily be converted between the two.

The problem isn’t the zoning. That can be fixed with literally a stroke of a pen. The problem is that the buildings were never designed for habitation, and so you run into issues with plumbing and windows. Sometimes these things are fixable, but usually at great cost, especially for newer construction.

Rezoning alone is insufficient. For traditional (but interestingly not technical) reasons, the designs of commercial and residential buildings are very different and converting between them in already built structures is going to be very costly.

going from office to residential is very expensive and is often more expensive than a complete tear down and rebuild.