Thanks guys. I spoke to the local town planner, he is optimistic that  the land can build 7-8 houses.
But I also spoke to the council and found out that there is an environmental draft which proposes to change the zoning of lands in my area. It could be effective soon after the state government signs off.
It is quite hard to make a call.

Question, I heard that normally in Sydney, the developers look for 150k per site as acceptable land cost, say in my case, 150 x 8 = 1.2m, that is to say they are likely to accept the price around 1.2m for both lands. I am not sure how reliable this calculation is.

Look forward to your thoughts.