Zaragoza took the player on loan from Milan in 2007 and exercised an option to buy him at the end of the following season, after he top scored for them, despite their relegation to the second division.
Media reports at the time said the deal had cost Zaragoza around 10 million euros. He was sold on to Real Betis in January 2009.
"Real Zaragoza and AC Milan have recently reached an agreement to restructure the repayments that remain from the transfer of Ricardo Oliveira," Zaragoza said in a statement on their website.
The club said the deal was in line with their attempts to reduce the size of their overall debt to manageable proportions over the next six years.
"The agreement reached between our club and Milan carries with it the suspension of any action taken before FIFA with regard to the said transfer," Zaragoza added.
Zaragoza, who won promotion back to the top flight in 2009, are one of a number of Spanish clubs struggling to make ends meet.
A recent study by Jose Maria Gay, a professor of accounting at the University of Barcelona and an expert on football finances, reported that the 20 La Liga clubs at the end of the 2008/09 season had total debts of 3.526 billion euros.
