is it possible to parse multiple chunks in a single nltk.regexp parser?

can grammar have multiple chunks define like this?

def parser(s):
    grammar = """
    NP: {<DT>?<JJ>*<NN>+}
    VN: {<VB.?><DT>?<NN>}
    """
    words = nltk.word_tokenize(s)
    tagged_words = nltk.pos_tag(words)
    cp = nltk.RegexpParser(grammar)
    chunked = cp.parse(tagged_words)
    print(chunked)
    for _ in chunked:
        if isinstance(_, nltk.tree.Tree):
            if _.label() == 'NP':
                print(_.leaves(), 'Noun Phrase')
            if _.label() == 'VN':
                print(_.leaves(),' a verbed noun')

The result do not include VN chunks

(S
  i/NNS
  need/VBP
  (NP a/DT project/NN manager/NN)
  who/WP
  knows/VBZ
  (NP c++/NN))
[('a', 'DT'), ('project', 'NN'), ('manager', 'NN')] Noun Phrase
[('c++', 'NN')] Noun Phrase