Australia and New Zealand have very similar health systems, so the overall process is quite similar and the degrees are recognised in both countries without any need for extra examinations which is a great bonus.
For both Auckland and Otago it takes 6 years undergraduate until you become a doctor, while for those who do a different undergraduate degree first it’s usually a 3/4 year year undergraduate degree plus 5 years of Medicine for a total of 8-9 years.
However, in NZ the 6th year of medical school is a Trainee Intern (TI) year in which you are paid a stipend of about $30,000 during the year, so for fair comparison NZ I would consider the total undergraduate process as more like 5.5 years rather than 6.
There is a lot more options here given there are so many medical schools. The shortest pathway is in Medical Schools such as Monash, Newcastle and Bond University which are 5 year undergraduate degrees, while some like The University of Adelaide and James Cook University are 6 degrees total, and The University of Sydney is 7 years since it is a double degree programme (3 years for a non-medical degree and 4 years for Medicine). Postgraduate medical schools in Australia also vary in being 4-5 years meaning it would be a total of 7-9 years depending on the length of your undergraduate and postgraduate degrees.
Keep in mind that across Australia, while the internship year is after medical school rather than before, it is still the equivalent of the 1st year House Officer role that medical school graduates from NZ go into. From there, progression as a junior doctor (House Officer) through to mid-level doctor (Registrar) and senior doctor (Consultant) is the same in both countries given that we share the same Royal Australasian Colleges for each of the specialties within Medicine. You can refer to this post for more detail on the progression beyond medical school which is the same for Australia and New Zealand
Local Graduates are Prioritised
While Australasian medical degrees are exchangeable as mentioned above, most hospitals prioritise local medical students above those coming from outside, so knowing where you want to live is still quite important in making your decision for which medical school to attend. For example, if you want to live in Melbourne, you would be best off studying at Monash or the University of Melbourne, for Sydney, at the University of Sydney, UNSW, Newcastle or University of Western Sydney, and for NZ, studying at Auckland or Otago. Off course some students still get accepted interstate in Australia or international between NZ and Australia, these are a minority and are usually stand-out candidates to have a chance.
Hopefully that answers your question, and for further information on Australia Vs NZ, this post also outlines some of the other differences in terms of entry pathways, lifestyle and career progression too.