it would n't have taken the protagonists a full hour to determine that in order to kill a zombie you must shoot it in the head 
(ROOT (S (NP (NP (PRP it))) (VP (MD would) (RB n't) (VP (VB have) (VP (VBN taken) (NP (DT the) (NNS protagonists)) (NP (DT a) (JJ full) (NN hour)) (S (VP (TO to) (VP (VB determine) (SBAR (IN that) (S (SBAR (IN in) (NN order) (S (VP (TO to) (VP (VB kill) (NP (DT a) (NN zombie)))))) (NP (PRP you)) (VP (MD must) (VP (VB shoot) (NP (PRP it)) (PP (IN in) (NP (DT the) (NN head)))))))))))))))
(ROOT (S (NP (NP (PRP ))) (VP (MD ) (RB ) (VP (VB ) (VP (VBN ) (NP (DT ) (NNS )) (NP (DT ) (JJ ) (NN )) (S (VP (TO ) (VP (VB ) (SBAR (IN ) (S (SBAR (IN ) (NN ) (S (VP (TO ) (VP (VB ) (NP (DT ) (NN )))))) (NP (PRP )) (VP (MD ) (VP (VB ) (NP (PRP )) (PP (IN ) (NP (DT ) (NN )))))))))))))))