So, I quoted you even though you asked not to
Anyway...
The council zoning restrictions and DA's (Development Applications) are for a building or for premises within a building, not for a business operating in those premises. And there is no registration for brothels (that would be the case in Victoria and Queensland), just a DA for the premises to be allowed to operate a brothel.
Thus, making the application is the responsibility of the owner of the premises, not the business, unless the owner also operates the business.
There a limits (depends on the council) on how many building/premises are approved to have a DA for the use as a brothel, and typically they are only approved for areas that are zoned as commercial, or mixed use. Pretty much never for residential only zones.
A lot of council areas in the Sydney area where brothels are allowed at all, nowadays have pretty much as many approved brothel premises as the councils would allow. Thus, good luck trying to get an approval for a new one.
This is why real estate that has an existing DA, when sold or leased, often goes way above the price of a similar premises which do not have a DA.
Every building needs a DA for the purpose of use, as the DA is related to the building code and zoning, so for example restaurants, retail shops, etc. And the building/premises need to meet the requirements for the purpose (like for example restaurants: sufficient toilets, fire escapes, maximum of patrons, requirements for kitchen facilities etc.)
Some of the specific requirements for brothels are: The spaces where the "business" is carried out, can NOT be on ground floor, which is why in most cases you need to hike up to the first floor (even if reception is on ground floor). Not within 100m from a church, school or daycare centre. Minimum 100 m from another brothel. And a few others, and these change depending on the council, as they decide how they do the zoning rules.
If there is a breach of the approved purpose of the DA (regardless of the business), first time results to a warning (and for example in restaurants, a requirement to fix possible fault in the kitchen etc.)
In the case of massage shops (which offer extra services and some that also openly advertise "erotic massage"), this yet again depends on the council how they treat this since there is no actual state legislation on it and prostitution in NSW is legal.
Most councils currently have a very pragmatic approach to it. And even those councils (they typically had a few counsellors of the overtly religious type) that a few years ago tried to close some massage shops and took them to court for breaching the DA, have pretty much stopped as the process of going to court costs a fair bit and they were knocked back by the judge with the notion "do you have proof?"
Anyway, since breaching a DA, unless there is harm due fire hazard etc, is not a criminal offence, the most that can happen is a fine or order to seize operating outside of the DA approval (in which case it may result on voluntary closing of the business and finding a new location).
The John and Jill in the room are not doing anything illegal (as long as everything done is consensual), so the worst that can happen to them is to be dragged to court as witnesses.
This of course may not be a desired outcome for example to those Johns who have a wife
Disclaimer:
All of the above, in general, is what the situation is in NSW. Other states have different legislation than NSW.
For example, NSW is the only state where prostitution is totally decriminalised. It used to be illegal.
In VIC and QLD it's technically only legal in registered brothels.