Find all regular files under $DIRECTORY_TO_PROCESS matching the case insensitive regex ".*\.$FILES_TO_PROCES" where $FILES_TO_PROCES is a variable and not matching the name pattern '$find_excludes' where $find_excludes is another variable, then print the files with null delimiter instead of newline
find "$DIRECTORY_TO_PROCESS" -type f -iregex ".*\.$FILES_TO_PROCES" ! -name "$find_excludes" -print0