The extension file name is not the issue.
It appears the NCE - Chemical Engineering Symbols extension was created from the VRT Network Equipment extension.
Inside the extension OXT file (ZIP) there is an XML file called description.xml.
The extension indentifier is the same value in both extensions causing a conflict in LibreOffice.
<identifier value="au.com.vrt.libreoffice.gallery.network" />
Since the identifier is the same LibreOffice thinks it is the same extension.
I changed this identifier value in the NCE extension and re-zipped the extension.
Installed and tested briefly - both extensions appear to be working.
This “forum” will not allow me to upload the file - too big (max. 1MB, file is 2.23MB).
So I uploaded it here:
If this solved your issue please check the checkmark at left.