From Wiki

The question is often asked whether it is possible to apply for a temporary visa such as a subclass 457 visa (work permit) while waiting for a permanent migration visa such as a subclass 175 (Skilled Independent) to be processed.

The answer is yes, provided that you understand the following:

• there is no guarantee of permanent residence being granted, and if not, you will have to return home; and
• you will be subject to 457_Visa_Restrictions while on a temporary visa; and
• whole family will need to do the Auckland_Shuffle (or return to home country, or go to Singapore) to be granted an offshore visa.

If you have already got a skill assessment, why not see if employer will sponsor for an migration visa through ENS? If you have already lodged a 175/176 Skilled migration visa application, you can switch to ENS free of a visa application fee.

ENS visas are top priority in processing terms, and as at March 2009, do not normally require the employer to "test" the labour market.