On grammatical class:

ke'a
pro-sumti: relativized sumti (object of relative clause).
ma
pro-sumti: sumti question (what/who/how/why/etc.); appropriately fill in sumti blank.
zi'o
pro-sumti: fills a sumti place, deleting it from selbri place structure;changes selbri semantics.
zo'e
pro-sumti: an elliptical/unspecified value; has some value which makes bridi true.
zu'i
pro-sumti: the typical sumti value for this place in this relationship; affects truth value.