Those moments when you discover a crucially important feature has actually been available for years! Apparently Blender has had support for PSD files since 2.70… It’s possible I discovered this in the past but forgot about it after trying to load a layered .PSD file and it not working. Which using layered .PSD files in Blender will fail unless you’ve saved the file with the “Maximize Compatibility” setting activated in Photoshop.
Upon discovering this I immediately began testing to see if I could integrate .PSD files into Zero Brush, sadly Blender does not include “PSD” as an image file type extension to save images out as directly, I’m guessing due to legal complications, so I can not add .PSD as an output option for saving ZB texture layers. You could create texture layers with Zero Brush, use the “Save To Folder” option to save your image layers externally as PNG or TIFF or something, open them up in Photoshop and save them out as PSD files, then manually change the textures or nodes to those PSD files… but that would suck to have to do all the time. I tried using some of Blender’s available extension output saving options (like TIFF and PNG) and then just faking it (having the code change the output file to say “.PSD” after saving the file), but Photoshop was not into opening those files lol.
You’re better off using Zero Brush’s .TIFF output option. When doing so you can easily use and reload layered .TIFF files and Photoshop treats these almost identically to .PSD files. Still, getting to use layered PSD files is awesome for working on environments and other things. Blender CAN save changes made to .PSD files while in Blender, so long as those files were imported initially as PSD files… just can’t save stuff created, or imported into Blender not as a PSD file as a PSD file.