The best way to do this is to follow the procedure the "dosdude1" has created.
Go to his website dosdude1.com.
For Catalina specific: http://dosdude1.com/catalina/
If you need a USB install for Windows 10, then do this from a PC/Laptop with Windows 10 running.
Go to the Microsoft site and create USB install media from there with the Microsoft "MediaCreationTool". This will result in a USB stick formatted with FAT32 and the installer files smaller then 4 GB!!!
Note: It is possible to do from macOS, but then you need a file splitter program for the large 4GB+ files in the ISO (You need to have a FAT32 AND not a exFAT to get it booting)..