I think you will need an on INPUT event to 'speak' zombie.
To understand zombie I think you may want something like this:

on ^*:TEXT:*:*: {
  var %text $strip($1-) 
  if %zkey isin %text {
    %text = $replacex(%text,!?!, z, ???, y, !!!, x, die, w, key, v, oof, $&
      u, gah, t, fla, s, fue, r, fel, q, fom, p, arr, o, arg, n, ack, m, $&
      urg, l, yumm, k, ommn, j, brains!!!, i, goo, h, gop, g, omnomm, f, $&
      slop, e, err, d, erg, c, ugh, b, uhh, a)
    echo -tbf $iif(#,$v1,$nick) $+(<,$nick,>) %text
    haltdef
  }
}
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