To explain, if we're talking about Cell Games Cell, then it's pointless to talk about his levels upon resurrection because it was stipulated that we're using an exact era of Cell against Piccolo. There's no Buu Saga Cell or anything after where he's resurrected (and thus can take advantage of the zenkai).
Also that even if Krillin or Piccolo killed him or incapacitated him for more than 10 seconds and he somehow has the ability to bring himself back, that's still a loss according to Board rules via 10-count, so zenkai would still be useless.