How can I mount a hybrid CD in macOS
A few things:
The most likely problem: Apple dropped support for the &quot;Mac OS Standard&quot; HFS file system in macOS 10.15 Catalina. (Catalina retains support for the &quot;Mac OS Extended&quot; HFS+ file system.) While HFS+ was introduced in 1998 with OS 8.1 and quickly took over common usage on hard drives, it includes a &quot;journal&quot; of file system operations that makes it difficult to use with read-only drives, so CD-ROMs continued to use HFS until they were replaced with DVDs which use a different file system altogether.
AFAIK, currently (August 2020) there are no good tools for reading HFS file systems under Catalina. A bunch of attempts at utilities that may mature over time, but nothing ready for prime time. Probably your best bet is to use a virtual machine running compatible software to read the files.

Using Virtual Box, I can see the Windows partition, but on MacOS I can’t.


In general, macOS will not show the Windows partition of a multi-format CD.
You cannot use the CD drive with Virtual Box and the host macOS at the same time. The drive gets attached to one or the other. I am not sure if quitting Virtual Box is enough to make it let go of the drive.


I cannot successfully mount the Apple Partition using either mount or diskutil, or at least with the options I have tried.

I cannot think of a time when Disk Utility could see the drive and partition but not mount it that I was also able to mount it successfully from the command line.
Nevertheless, if you are going to try to mount the partition from the command line, you want to mount the Apple_HFS partition, which in the output provided is listed as disk7s1s2, so the command would be
diskutil mount readOnly disk7s1s2