I think I prefer
Zelda. Zerelda is not horrible but it doesn't have the most pleasing sound to it either.
Zelda is spunky and cool, it also works with a common or old fashioned middle name.
As for Zerelda I find this so old fashioned (unlike
Zelda which is ready for a comeback) that I wouldn't pair it with anything that is still only slightly dated so no Zerelda
Margery or Zerelda
Agnes for me, in combination they really sound like someone's great aunt. I like
Margery and
Agnes paired with other names.
Cleo is spunky so that works for me or even
Violet or
Vivian (prefer this spelling).
Vivian definitely gives Zerelda some life with its fresh, happy sound and meaning. Zerelda
Viviana is good too even though they both end in A.