nothing short of a masterpiece -- and a challenging one 
(ROOT (NP (NP (NP (NN nothing)) (ADJP (JJ short) (PP (IN of) (NP (DT a) (NN masterpiece))))) (, --) (CC and) (NP (DT a) (JJ challenging) (NN one))))
(ROOT (NP (NP (NP (NN )) (ADJP (JJ ) (PP (IN ) (NP (DT ) (NN ))))) (, ) (CC ) (NP (DT ) (JJ ) (NN ))))