WITHOUT FORMATTING WITH APACHE POI ALL IS FINE AND ZK WORKS FINE!
WITH FORMATTING WITH APACHE POI HAPPENS THAT:
After the show of the file in the web page, after the change of a value in one cell the browser gets busy for 10 seconds. After this period, the browsing is ok but after one another change of a value in on cell the problem is the same.

THIS IS THE FUNCTION APACHE POI THAT CREATES THE PROBLEM:
-->style.setWrapText(true);
cell = row.createCell(j);
cell.setCellStyle(style);

WITHOUT THIS FUNCTION ZKS WORKS FINE BUT THE SHEET IS BAD FORMATTED.
AS ATTACHMENT I SEND YOU TWO EXCEL FILE : ONE FORMATTING (PROBLEM WHIT THE PERFORMANCES) AND ONE NOT FORMATTING (FINE)

THANK YOU!