CDDZ format is used for the default document format in a diagramming software called ConceptDraw and cddz to vsdx conversion is typically searched by users that are looking for a way to convert ConceptDraw files to Microsoft Visio.
This is doable with the original software as it supports export to VSDX format just fine, but extremely unlikely that any other software can be used for this.
Updated: October 9, 2023