Zombies are questions with no upvoted answers. I came up with this SEDE query to find answers with zero votes on questions that have no accepted answer and no answers with greater than zero score. In other words, answers on questions that show up on the Unanswered tab, until the answer receives an upvote.

DECLARE @username AS NVARCHAR(60) = ##DisplayName:string? ##;
DECLARE @userId AS INT = ##UserId:int?-1##;

SELECT TOP 100
  u.Id AS [User Link],
  a.Id AS [Post Link],
  a.CreationDate
FROM Posts a
  JOIN Users u ON a.OwnerUserId = u.Id
  JOIN (
    SELECT q.Id, MAX(a.Score) MaxAnswerScore
    FROM Posts q
    JOIN Posts a ON a.ParentId = q.Id
    WHERE q.AcceptedAnswerId IS NULL
    GROUP BY q.Id
  ) q
  ON a.ParentId = q.Id
WHERE 
  (@username = '' OR u.DisplayName = @username)
  AND (@userId = -1 OR u.Id = @userId)
  AND a.Score = 0
  AND q.MaxAnswerScore = 0
ORDER BY a.CreationDate DESC

Is there a better way to write this? Can it be improved?