Quickest way: buy one.
Starting from scratch in Victoria, it is easy, all you need is planning permission and a licence from DSE. However, from personal experience:
Planning permission took us 3 years. Of course you will have to find an area where what you plan is an allowed usage. It is getting harder to find sutably zoned land in many areas that you might want to set up in.
Then you will have to deal with DSE (no damage to the environment), EPA (waste water disposal) and Vicroads (traffic issues). Things will happen like, when we wanted to build our wetland it was classified as a dam, when we discussed our sewage system it became a wetland again. Yes each classification resulted in more servere requirements against classification the other way round. We missed out on this, but today we would have had to have the property surveyed by the local aboriginals for cultural relics. And if you plan to dig more than 300mm into the ground they will want to hang around to make sure you don't dig up anything significant. I am sure there are others I have forgotten. All of the above you pay for of course.
Council will advertise your application. This may result in objections, in our case only two, and their attempts to get others to support their objection was rejected by our other neighbours. But if you want exotics I imagine you might have an entirely different experience. As I said it took us 3 years (they did change the planning scheme halfway through) and we did have broad support form the Council and the local community.
Once you have planning permission you can build your zoo. DSE have a number of requirements for issuing a licence, the most servere is that they must inspect the enclosures before they issue the licence. (Interestingly they don't ask for any evidence of your knowedge of animal husbandry). We were lucky in that many of the animals we wanted we could hold on private licences anyway. Different story for exotics, so I imagine you would have to have somebody with an appropiate licence hold your animals until you get a licence. Could be difficult.
Getting animals is largely a process of building relationships with the people and institutions who already hold them. There are dealers overseas who you can buy exotics off, but importing is a long-winded and expensive process.
Lastly some financial advice. Make sure you marketing budget is at least 3 times what you think is reasonable, and don't expect to make a profit for at least 5 years.
Hope that helps.