You are mostly correct. Zoning laws can include exemptions of certain laws when land is zoned for certain use such as noise pollution laws and so on on ag and commercial use. Zoning laws are also set at the state, county, township and local level, but of course each is enforced by your most local form of government. In turn, these exemptions outlined by zoning laws are also approved by the same body that approves the local ordinances.
So basically let's say you live in Sunbury. Sunbury has a noise ordinance, but zoning laws will say that if you are zoned for this, this and this, you are exempt, if you are zoned for this this and this, your noise ordinance differs in this fashion.