Jose Riga has told Blackpool chairman Karl Oyston to deliver on his promises after the two forged an uneasy truce.
Wilfried Bony claims to be fully focused on Swansea at the end of a summer in which his future was called into question.
The Colombia international, 26, moved to San Siro on a season-long loan last summer and his performances for the Rossoneri - who finished third in Serie A - have earned him a three-year contract in northern Italy.
A statement published on acmilan.com read: "AC Milan wishes to communicate they have made the signing of Cristian Zapata from Villarreal permanent.
"The defender's contract will run to June 30, 2016."
Zapata, who previously spent five years in Italy with Udinese, has made 28 appearances in all competitions for Milan.