Yes he can use Mokuton as he gains the abilities of the body he took over, and Zetsu had Mokuton, but its going to be much weaker than Obito and Madara's, and Yamato's.
its not clear yet.. people shouldnt really be saying yes or no since we have no idea.. he has only just obtained the body however i believe that he should gain zetsu's abilities but we will have to wait and see