My guess is that you do not have the 'Z' drive mapped on the
CF server. On your second example, the UNC name isn't formatted
quite right. Instead of the 'D:\' in front of the IP address, try
'\\' instead. So assuming you have a share on that server named
'Public', try using:
"\\192.168.1.10\Public\Installs\my_data.txt"