alternative binary-layer function

here is a sketch for an alternative "binary-(or element-)layer-FUNCTION

(defun element-layer (lists &key (rnd nil))
  (let ((lists (if (null rnd)
                 lists
                 (rnd-order lists :list t))))
    (car 
     (last 
      (loop for x in (rest lists)
        with list = (car lists)
        collect (setf list (loop for i in list
                             with cnt = 0 
                             when (equal i 0)
                             collect (nth cnt x)
                             and do (incf cnt)
                             else collect i)))))))
  

(element-layer  (list  '(1 0 0 1 1 0 0 1 0 0 0 0)
                       '(0 2 3 0 4 5 0 6 0 7 8 0)
                       '(11 12 13 14 15 16 17))
                :rnd nil)

 => (1 11 2 1 1 3 12 1 4 5 13 6)

;;; hierarchic: every 0's will be replaced by the values from the next/sub-list...