Notwithstanding section 5 of chapter 40A of the General Laws or any other general or special law, charter provision, ordinance or by-law to the contrary, during the governor’s March 10, 2020 declaration of state of emergency related to COVID-19 and for a period of 30 days after the termination of the state of emergency, the board of selectmen or select board in a town having a town meeting form of government may, by a 2/3 vote of the full board, adopt or amend any zoning by-law to maintain compliance with the National Flood Insurance Program and to incorporate updated flood hazard areas as required by the Flood Insurance Rate Maps prepared by the Federal Emergency Management Agency; provided, however, that said action by the board of selectmen or select board may only be taken following a public hearing on any such zoning by-law or amendment conducted by the planning board pursuant to section 5 of chapter 40A of the General Laws; and provided further that no zoning by-law or amendment acted unfavorably upon by the board of selectmen or select board shall be precluded from being considered by town meeting following the termination of the state of emergency. The effective date of any zoning by-law or amendment adopted pursuant to this act shall be the date of approval by the board of selectmen. Notwithstanding section 32 of chapter 40 of the General Laws, the time for review by the attorney general shall be 30 days from the date of submittal of the by-law by the town clerk.