A major amendment shall not be made effective unless a public hearing has been held upon it in accordance with Article 5 (commencing with Section 59641) of this chapter for the establishment or institution of a marketing program, and the director makes both of the following findings:
(a) The amendment is in conformity with the applicable provisions and procedures of Article 5 of this chapter.
(b) The amendment is assented to in writing in the required percentages prescribed in Article 9 (commencing with Section 59851) of this chapter.