As StoneyB says, these are just old spellings of the two words smite and pieces. Most resources (e.g. your average dictionary) will not list all the different spellings a word had throughout history for the simple reason that it takes up a lot of space (many words were spelled in dozens and dozens of different ways).
There are two resources I know of that list historical spellings of words: the Oxford English Dictionary (OED) and the Middle English Dictionary (MED).
You will not be able to access the OED without a subscription, but it does mention both the spellings. It says that the smyte spelling was used from the Middle Ages up until the 1600s. Also, the relevant definition of smite for your passage is:
trans. Chiefly with adverbial complement, as asunder, into pieces, in two, etc.: to cut, chop, or break apart, into pieces, etc.
You can also see this spelling attested in the MED (unlike the OED, anyone can access the MED).
Both the OED and the MED have quotations that use the pecys spelling for pieces. (However it is bizarrely enough not listed in either dictionary's forms section.)