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You have two options here. Typically enforcement authority is discretionary to the government as part of their police powers and they have the power to enforce or grant waivers. Here it seems they are stuck in the middle and are not performing their duties in accordance with the law. Therefore, option 1 is that since the zoning board is ignoring your complaints, your next option is filing a petition for writ of mandamus
in the court and get the court to order the board to perform their job and enforce the laws on this matter.
Your second option is to file a suit directly against the neighbor for nuisance and encroachment in contravention to the zoning ordinances and his refusal to even comply with the waivers granted by the zoning.
Thus, you have two options here to pursue this matter, but both require you to go to court to get your relief if the board refuses to act and stop this individual from building his illegal and crooked garage (which you could also argue is a danger to the building inspector since it is not even).
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