The report was prepared for former president Thabo Mbeki by Justice Sisi Khampepe and Justice Dikgang Moseneke after they were sent by Mbeki to observe the elections.
Last week the North Gauteng High Court ordered the presidency to hand over the report to the Mail & Guardian. The newspaper has fought for the past four years for its release.
Zanu-PF officials said the report contained information supplied in confidence by people close to President Robert Mugabe and its release might prove politically awkward for party officials who supplied the information.
The information could relate to Zanu-PF's complicity in violence, election misconduct that bordered on manipulating the process in favour of Mugabe and confidential information about how Mugabe conducted party affairs, insiders said.
The two insiders, who are central committee members of the party, said Zanu-PF is also worried that the report might finger officials and destabilise the party ahead of elections.
Analysts said the report was a reminder of the recent WikiLeaks scandal that created widespread problems within Mugabe's party.
WikiLeaks identified several ministers, retired and serving military generals and Mugabe confidantes who allegedly held secret meetings at the United States embassy where they revealed their lack of confidence of Mugabe's leadership.
Professor Brian Raftopolous, a developmental studies academic, said the South African report was similar to WikiLeaks.
There could be a "gnashing of teeth" in the party if there was information in the report supplied by Mugabe's confidantes that expressed reservations about the manner in which that election was held.
Raftopolous said it was important for Zimbabweans to know what the report contained "so that the wrongs committed are known and addressed," especially in the context of the elections this year.
Political analyst Charles Mangongera said the report was potentially damaging for Zanu-PF as it was likely to confirm the use of sanctioned violence in the 2002 presidential election.
Mangongera said Zanu-PF's anxiety about the release of the report was understandable because the "last thing the party needs is division ahead of elections". It would be "politically damaging" for any official to be mentioned.
However, Mangongera said there was hope for those mentioned that the party would not sanction them because it had not disciplined any of the officials involved in the WikiLeaks reports.
SA government 'uncomfortable'
A Zanu-PF MP said, however, that no action had been taken by the party over WikiLeaks because, in that case, the motive of the foreign diplomats was questionable, but in the case of the Khampepe report, "it will be difficult for the party to ignore it as the views and information supplied by the judges will be taken as credible".
A South African diplomat based in Harare said the South African government was not comfortable with the release of the report because it could throw the country's mediation role on behalf of the Southern Africa Development Community into disarray as "no one may want to confide in South African officials again".
Civil society has enthusiastically welcomed the judgment.
Irene Petras, the executive director of the Zimbabwe Lawyers for Human Rights, said the contents of the report were "significant insofar as they may be able to confirm long-standing allegations of electoral malpractices, state complicity in violations and/or electoral fraud".
She said the "continued resistance by the South African government to comply with the order to release the report could lead to negative conclusions being drawn about the contents of the report and thus fuel presumptions that there is something to hide".
In last week's ruling, Judge Joseph Raulinga said: "Without disclosing the contents of the report, I can reveal that the report potentially discloses evidence of substantial contravention of, or failure to comply with, the law."
Raulinga ordered the report to be released within 10 days of his February 14 ruling.