Zipping a .tgz file corrupts the file

[caiismyname]

If I run yarn pack (which outputs a .tgz), then read in the the resulting file
let content = fs.readFileSync("package.tgz", "utf8")
then zip it
zip.file("package.tgz", content)
, trying to unzip the resulting file once the overall package is unzipped results in a corrupted .tgz whichtar -xzf is unable to unpack.