1. You might be talking about another parcel, this is what I get about your tracking number above:
Number: RS151139253CN
Package Status: Not Found
Destination Country: Unknown
Origin Country: China

2. The above tracking number is a valid tracking number, just in case you ask.

Hope this help.

1. This is the full tracking of your parcel:
Parcel No.RS034514375CN tracking result
2016-07-22 15:39:55.0 佛山city Post Office parcel 集邮局 received
2016-07-22 17:22:52.0 佛山city Post Office parcel 集邮局 customs scan
2016-07-22 20:09:21.0 leaving 佛山city Post Office parcel 集邮局 ，next station 南海
2016-07-23 13:52:06.0 Guangzhou Transit Station export security scan
2016-07-23 15:02:42.0 Guangzhou Transit Station export customs cleared

2. Even if you don't see any tracking it does not mean the parcel is not traveling. Maybe on it's way to the Airport Warehouse.

3. Also please take note that lately there has been some closer security check in Guangzhou Airport so that might delay your parcel.

4. China Post Airmail Parcel Estimate Arrival Time for New Zealand can be found here:
http://track-chinapost.com/China_Post_Arrival_Time_Stat.php

5. May I suggest you keep tracking your parcel for new scan.

Hope this help.