Hi Cateb,
What one of the new zones does is lock some properties up from not being able to be subdivided into more than 2 lots. So, if your strategy was for 2 units, that is still a valid strategy.
Whether 2 dwellings can be achieved on any given lot depends on the individual features of the site and the specific planning controls, same as before really. Frankston are looking at bringing in new restrictions in some areas, but these haven't been approved yet.
I would recommend that you get advice once you have narrowed down to a property so that site specific details can be taken into consideration.