Matrioska Sudoku

[qq8]

Can someone explain the rule(s) for solving this variation? I looked but could not find any info on this.

Thanks in advance for any help.

[emilio]

sono due schemi collegati.
Le celle del 5° settore (centrale) del 1° schema sono colorate e vanno a distribuirsi nelle celle centrali di ogni settore nel 2° schema.

Two schemes are connected.
Cells, Sector 5 (center) of 1 scheme are colorful and are to be distributed in the central cells of each sector in the 2nd diagram