Rezoning isn’t a quick process, and there are no guarantees. “Sometimes councils won’t rezone because the land is too fragmented and needs consolidation,” Coutts says. “It can easily take four to five years. Some landowners don’t have that time, so it can be a very daunting and upsetting process. You can see why they say ‘just sell it and let’s get out of here’. But if you can wait and manage the process effectively, the rewards can be considerable.”

One of the best ways to do this is by using Google Earth (which is free) and the topography map from Earth Point (which is also free). With Google Earth, you can search for your property (using the address or coordinates) and zoom in using your mouse buttons and the control/command and shift keys on your keyboard. This will allow you to tilt the earth so you can see precisely where all the hills and valleys are in your area. 
This question is out of my realm...but I'm curious why you decided that the current developer is not interested in your property? If his equipment is close... it might not be that hard to deal with your property. Since you already have a house on it, I can assume there's sewage, water, electricity, etc... So your land doesn't need to really be developed, but they could build something nice on it.
It depends on a number of factors, are you trying to find cash buyers for your land, what is your time frame to sell the land, and are you trying to get full market value for the property, and how much work do you want to do to sell it? Depending on your answer to those questions the method by which you decide to list and market the property is going to be different.
If you are a potential buyer looking to purchase property directly from a seller - Many properties are available across the country and outside of the U.S. including vacant residential lots, large acreages, homes and ranches, hunting and fishing properties, investment properties, land ready for development, commercial buildings and much more. View Listings.

Consider your own needs when pricing, and understand how pricing could impact buyers’ interest. When selling real estate, you sometimes have to choose between getting the highest price and possibly selling quicker. Plus, your pricing may be influenced if you need to sell for financial reasons. In addition to your own situation, pricing your property ultimately requires an understanding of the land market as a whole, why people are buying lots or land in that area and who these people are. A good real estate agent with land expertise can help greatly in this process.