euclid-distribute-zeros   scheme

(define euclid-distribute-zeros
  (lambda (dst-undst)
    (let loop ((out '())
               (dst (car dst-undst))
               (undst (cadr dst-undst)))
      (if (or (null? dst) (null? undst))
          (append (list (reverse out))
                  (if (null? dst) '() (list dst))
                  (if (null? undst) '() (list undst)))
          (loop (cons (append (car dst) (car undst)) out)
                (cdr dst)
                (cdr undst))))))