has bitten off more than he or anyone else could chew 
(ROOT (S (VP (VBZ has) (VP (VBN bitten) (PRT (RP off)) (NP (NP (JJR more)) (SBAR (IN than) (S (NP (NP (PRP he)) (CC or) (NP (NN anyone) (JJ else))) (VP (MD could) (VP (VB chew))))))))))
(ROOT (S (VP (VBZ ) (VP (VBN ) (PRT (RP )) (NP (NP (JJR )) (SBAR (IN ) (S (NP (NP (PRP )) (CC ) (NP (NN ) (JJ ))) (VP (MD ) (VP (VB ))))))))))