@pendean @john.vellek

Unfortunately AutoLISP routines you attached will not work in AutoCAD for Mac as they both use Visual Lisp functions which are not available on Mac.

I attached another FLATTEN routine which works on Mac (I modified it slightly to make fully compatible with AutoCAD for Mac), but it was written in 2000 and has some restrictions:

1/ It sets the Z-coordinates of these types of objects to 0 in the World Coordinate System:
"3DFACE" "ARC" "ATTDEF" "CIRCLE" "DIMENSION"  "ELLIPSE" "HATCH" "INSERT" "LINE" "LWPOLYLINE" "MTEXT" "POINT" "POLYLINE" "SOLID" "TEXT"

2/ FLATTEN doesn't flatten objects nested inside of blocks. (You can explode blocks before flattening. Alternatively, you can WBLOCK block definitions to separate DWG files, run FLATTEN in each of them, and then use INSERT in the parent drawing to update the block definitions. Neither of these methods will flatten existing attributes, though.
3/ FLATTEN flattens objects onto the Z=0 X-Y plane in AutoCAD's
World Coordinate System (WCS). It doesn't currently support flattening onto other UCS planes.

To run FLATTEN, load it using AutoCAD's APPLOAD command, 
Once you've loaded FLATTEN.LSP, type: FLATTEN