Whether or not a special exception or a variance has been granted therefor, no improvement shall be made or placed upon any land and no change in the location or ground area covered by any improvement shall be made until a zoning permit shall have been issued specifically therefor. No use shall be made in an industrial district and no customary home occupation shall be permitted until a zoning permit shall have been issued specifically therefor. As used in this section, the term "improvement" includes a swimming pool, and a zoning permit shall be required therefor, but does not include other accessory improvements, which are neither buildings nor signs, and a zoning permit shall not be required therefor.