Many custom materials require specific plugins, such as the Custom Shaders Patch (CSP) for Assetto Corsa, to render correctly.
Before extracting, scan the file using a service like VirusTotal to ensure it does not contain malicious scripts, especially if it was sourced from an unverified modding site. RCL7cumaterial.zip
Knowing the software it's intended for or the community it came from would allow for a much more specific breakdown. Many custom materials require specific plugins, such as