Isla made just 11 league appearances last season and is currently a target for Inter, but Marotta has insisted the Chile international hopes to remain with the reigning Serie A champions.
"Isla is our player,” the official told Sky Sport Italia. "I’m not denying Inter’s approach for him, but, with no substitute, he will remain ours.
"He’s told us that he would like to stay and, with boss Antonio Conte’s blessing, he is a Juventus player."
As for Napoli defender Zuniga, who played a prominent role in his side's second-placed Serie A finish last term, Marotta added: "We have a good relationship with Napoli and we accept that they will not be selling him."
The Italian went on to explain that Juve are unlikely to target further signings, with trimming their bloated squad now the priority.
"I don’t think we’ll sign anyone else. We’ve added to sections of the team that needed it such as the attack and defence," he added.
"We brought in a lot of players at the start of the summer, we have built a competitive team. In these tough economical times for Italian football, we have invested well.”
“We have an attack that needs reducing because six players of that level are a lot. We want five, perhaps with a youngster to develop.
“The hope is that we find a positive solution for us. The requests will need analysing, but the desire of the player is more fundamental than that of the club.”
