I am surprised that no one knew the answer for my question however i got following reply from citizenship office, hopefully it may help others.
You may be eligible to apply for New Zealand citizenship up to four months early (after holding your residency for four years and eight months), if you have already met the presence requirement. To be eligible to apply, you need to have been present in New Zealand for at least 1350 days over the last five years immediately before you apply. In each of those five years, you need to have been present in New Zealand for at least 240 days. Once you have met the above criteria, you do not have to wait for the remaining four months before you are eligible to apply. Therefore, if you are currently in your fifth and final year, as soon as you meet the presence requirement this year, you are eligible to apply. This means that you may be able to apply up to four months earlier than 06 March 2018.
Assignment to a case officer will take approximately two to three weeks if you send your application through the mail. If you submit your application via an appointment with one of our case officers, that person will process your application. Most applicants will be advised of the outcome from their application within two months of submitting a correct and complete application. After your citizenship application has been approved, it normally takes two to four months for you to be allocated to attend a ceremony in your area. The waiting time to be allocated to a ceremony is dependent on where you live and the schedule of the local council.The Department will send you a formal invitation two to three weeks before your ceremony date with details of the time and venue.