Go4zgate2.0.tar.gz is broken. The real archive should look like this:
ftp/pub/network/gopher/Unix/gopher-gateways/go4zgate:
total 1054
-rw-r--r-- 1 root wheel 538710 Apr 26 1994 Go4zgate1.0.tar.Z
-rw-r--r-- 1 root wheel 531253 Jun 15 1995 Go4zgate2.0.tar.Z
-rw-r--r-- 1 root wheel 205 Jun 15 1995 Readme