Many people on here do have chickens where they are not allowed. They choose one of two routes:
1) Get them anyway and beg for forgiveness later when caught. This means if you go this way they can take your chickens away when you get caught even if you are fighting them. Some are still able to keep them but most are not.
2) Fight to get the rules changed first. If you do this, than you will be following the law with little risk but a big fight.
Are you in city/town limits? This is usually where the zoning doesn't allow them. Go to city hall and they can tell you what you are zoned for right away. They would have a list and a map of it. Do any of your neighbors have any larger livestock (cow, horse, goat)? If so, you are listed as either agricultural or unzoned and both allow chickens. Either route that you choose, I would suggest you find out what you are zoned for beforehand so that you know what you are getting yourself into. 4 acres seems like a lot not to be able to have them in my mind. Good luck!