изменить порядок полей

/**
 * Change field position in checkout page
 */
add_filter( 'woocommerce_default_address_fields', 'mrks_woocommerce_default_address_fields' );

function mrks_woocommerce_default_address_fields( $fields ) {

    // default priorities: 
    // 'first_name' - 10
    // 'last_name' - 20
    // 'company' - 30
    // 'country' - 40
    // 'address_1' - 50
    // 'address_2' - 60
    // 'city' - 70
    // 'state' - 80
    // 'postcode' - 90

  // e.g. move 'company' above 'first_name':
  // just assign priority less than 10
  $fields['postcode']['priority'] = 41;

  return $fields;
}