Upon the date fixed in the ordinance of annexation, the area annexed shall become a part of the city. Upon the date fixed in the ordinances of annexation and adoption of the proposed zoning regulation, the area annexed shall become a part of the city, and property in the annexed area shall be subject to the proposed zoning regulation, as prepared and filed as provided for in RCW
35A.14.330 and
35A.14.340. All property within the territory hereafter annexed shall, if the proposition approved by the people so provides, be assessed and taxed at the same rate and on the same basis as the property of such annexing city is assessed and taxed to pay for the portion of indebtedness of the city that was approved by the voters.