If you get Merits in year 13 for NCEA level 3, does that mean you can still apply and get those credits?
As reference, the NZQA calculates an Interstate Transfer Index, which is used by the Australian Tertiary Admissions Centre to determine the equivalent ATAR. See more here: https://www.nzqa.govt.nz/qualifications-standards/awards/university-entrance/entrance-to-australian-universities/
Broadly speaking, there needs to be a check on course equivalents and course requirements per university in Australia you intend to submit an application for. To your question, Merit is the minimum consideration for credit achievement.
See the following for a number of universities:
University of Melbourne (helpful tables and case study): https://study.unimelb.edu.au/how-to-apply/undergraduate-study/domestic-applications/entry-requirements/equivalent-qualifications-to-the-vce/how-youre-selected-applicants-with-ncea