How to batch convert state plane coordinates to lat long with multiple SPC Zones?

Here's a partial solution, and I think there might be a bug, but here goes.

Given a CSV that looks like this:

You can load the CSV into QGIS and use the DB Manager Query window to perform SQLite / sql spatial functions on your data.

select 
c.*
, make_point(c.x, c.y) as geom 
from libraries_denver_csv as c

This basically turns the two coordinate values into a geometry object that can be drawn on the map:

Now what I thought would be possible would be to simply apply the ST_Transform / Transform function on that constructed geometry and use the value in the spc_zone column to serve as the SRID integer for that transformation.

However, I keep getting a NULL response, and can't figure out why - perhaps this doesn't exactly work in SQLite - and if anyone can add some info, I would appreciate it (as this question came up this morning on a local GIS forum as well):

select 
c.*
, make_point(c.x, c.y) as geom 
--test with value from spc_zone column
, Transform((make_point(c.x, c.y)), cast(spc_zone as integer)) as geom_transform
--test with single known SRID value to apply for all records
, Transform((make_point(c.x, c.y)), 3857) as geom_transform

from libraries_denver_csv as c

But unfortunately this consistently yields a NULL response:

Does anyone know why that might be happening?