Extract words containing diphthongs om and eu, solution atom and nucleus

(defun list-of-rep (text &optional res)
  (let ((res nil))
   (dolist (w (setof text) res)
     (let ((c (count w text)))
       (when (> c 1) (push (list w c) res))))))
 
==> list-of-rep
 
(list-of-rep '(The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons.The electrons of an atom are bound to the nucleus by the electromagnetic force.))
 
==> ((The 4) (by 2) (nucleus 3) (ATOM 2) (of 5) (charged 2) (a 4))

(defun is-part (lst1 lst2)
  (let ((l1 (length lst1))
        (l2 (length lst2)))
    (cond ((> l1 l2) nil)
          ((equal lst1 (subseq lst2 0 l1)) t) 
          (t (is-part lst1 (cdr lst2))))))
 
(defun list-of-dift (text &optional res)
  (let ((res nil))
   (dolist (w (setof text) res)
     (when (or (is-part '(o m) (explode w))             
               (is-part '(e u) (explode w))) (push w res)))))
 
(list-of-dift '(The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons  The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons The electrons of an atom are bound to the nucleus by the electromagnetic force ))
 
==> (electromagnetic nucleus ATOM neutrons neutral atomic)