Code:
alias -l isdivzero { 
  if (!$regex($1,/\d[^+\-*\^%/]*/[ ()]*0++(?=[^1-9]|$)/)) {
    if ($lf isin $regsubex($remove($1,$lf),//[^+\-*\^%/]*(\d++[^+\-*\^%/]*(?:[+\-*\^%/][^+\-*\^%/]*\d++\51*)+)/,$iif(!$calc(\t),$lf))) { return 1 }
  }
  else { return 1 }
}
alias calc2 { return $iif($isdivzero($1),$null,$calc($1)) }