Whenever stdout needed to be used as a command argument, xargs is the answer. In this sample the output comes as last argument to xargs.
cat filelist.txt | xargs zip files.zip
Supposing filelist.txt a source of file names:
echo dir1/file1.cfg > filelist.txt
echo dir2/file2.log >> filelist.txt
echo dir2/dir3/file3.txt >> filelist.txt
