It looks like that vcd to iso conversion is in majority of cases related to conversion of various types of .vcd filesto standard ISO format, something that can be achieved directly with some disk image management programs.
Unfortunately, most of these utilities are not available for Mac, so a viable alternative is to use the Windows app in some virtualized environment, for example Parallels Desktop in order to convert vcd to iso.Open VCD file Open ISO file
A powerful CD/DVD-image-file editor, CD burner, and CD/DVD-backup tool
Application used to manage DAA and other disk images
Roxio Toast 11 Titanium makes disc burning, DVD copying and video conversion as easy as drag, drop and go
One of the disk image handling utilities and the default program for ISZ images
A CD/DVD/Blu-ray handling utility