The 41-year-old coach will depart Camp Nou at the end of the season after four successful years at the helm of the club to take a one-year sabbatical from football.
Guardiola's decision has earned Barca much criticism from former president Joan Laporta, who said that the club did not do enough to keep the coach, but Zubizarreta has guaranteed that is not the case.
"I am not one to contest Laporta, but we did everything we could to keep Guardiola," he explained to Esport3.
The former goalkeeper then hit out at Real Madrid assistant coach Aitor Karanka, who said that La Liga "existed before Guardiola and will continue to exist after him".
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"I do not understand Karanka's comments - acknowledging the exceptional work of a person is something basic," he added.
"I was delighted when Guardiola said that Karanka's remarks were obvious."
Zubizarreta went on to dismiss suggestions that Barca have a deal in place to make Valencia left-back Jordi Alba their first summer signing.
"I would like to deny that we have met with Jordi Alba and that there is an agreement in principle," the Barca director explained.
"I respect Valencia."
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