Hello GAN, thanks for your answer, look please on the declarations in my program
unit data;
{$mode objfpc}{$H+}
interface
uses
Classes, SysUtils, mysql55conn, sqldb, db, FileUtil, ZConnection, ZDataset;
___________________________________________________________________
unit main;
{$mode objfpc}{$H+}
interface
uses
Classes, SysUtils, mysql55conn, sqldb, db, FileUtil, DBDateTimePicker, Forms,
Controls, Graphics, Dialogs, ComCtrls, ExtCtrls, Menus, DBGrids, DbCtrls,
StdCtrls, DBExtCtrls, Types, data;