Falsify brief truths
Jelly, 8 bytes

ṣ0¬¬M¦j0


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How it works

ṣ0¬¬M¦j0  Main link. Argument: A (list of Booleans)

ṣ0        Split at zeroes. This leaves a 2D list of ones.
  ¬       Negate each 1, replacing it with 0.
     ¦    Conditional application:
    M       Yield all maximal indices.
            In lexicographical list comparison, a shorter list of zeroes is less
            than a longer one, so this identifies the longest runs.
   ¬        Negate the items in those lists, changing zeroes back to ones.
      j0  Join, separating by single zeroes.