as the title says, i hope this is self-explanatory. It used to be possible (in v5) to have a material be invisible to Z-depth (for archviz with a lot of glass, this is kinda essential).
Not sure when, or how, this was decided to be removed, but I really hope you can bring this back, so I don't have to render a separate z-depth pass for every single view I render (roll-eye emoji).
I hope I am explaining this problem accurately, but please refer to this thread for the same issue:
https://forum.corona-renderer.com/index.php?topic=30661.msg177702#msg177702