@Piyush RoutrayNot sure I am clear with what you mean by "I intend to have a separate NiFi cluster than the HDF cluster".
Are you installing just NiFi via command line?
- You can install NiFi using command line and utilize the embedded zk.
http://docs.hortonworks.com/HDPDocuments/HDF2/HDF-2.0.1/index.html
When you get to the download HDF section of the "Command Line Installation" documentation, go to the bottom of the list to download just the NiFi tar.gz file.

The relevant docs for this are found here:
http://docs.hortonworks.com/HDPDocuments/HDF2/HDF-2.0.1/bk_administration/content/clustering.html
http://docs.hortonworks.com/HDPDocuments/HDF2/HDF-2.0.1/bk_administration/content/state_providers.ht...
Are you trying to install NIFi via HDF's Ambari?
- The Ambari based installation of HDF will install an external ZK for you and setup NiFi to use it for you.
Thanks,
Matt