The obs-virtualcam plugin does not provide audio. As musicalsam said, you can just have it capture all computer audio. If you want greater control, you'll need to use either VBAudio VAC, or Voicemeeter to capture and route the audio as you like.
I just tested this and found out that on the advanced settings of zoom I can share only the desktop audio which fixed the audio delay I was having using virtual audio cables, but I still hear a robotic sound all the time, even when I'm not talking. I have played with all the obs audio filters with no success. The only way the noise disappears is by muting the microphone.
Don't know if this is of importance but the audio and video that comes into obs comes from a vlc streaming from a remote computer over the internet into obs using a vlc source. Opening that stream on the obs computer with vlc works fine, the audio sounds ok, its just when it goes through obs and then into zoom.
And to complicate things a little bit more, I'm remotely connecting to the computer at work that has obs using anydesk, so I cannot test how is obs sound working on that computer, only through the zoom session. But as I said, the audio works fine when connecting to the vlc stream on the obs computer with vlc, so this last part does not seem to be the issue.