If you mean zoning that requires first floor retail or whatever, sure. But mixed use zoning also means zoning that just doesn't ban small business, multi-family housing, and single-family housing coexisting on the same block.

The causality in your statement is backwards, because the lack of the latter kind of zoning is exactly what prevents inner suburbs from densifying organically. The current zoning in most of (at least US) suburbia is what artificially caps density.