Add migration - Both Entity Framework Core and Entity Framework 6 are installed

I have a solution with multiple projects one of them with EF 6 and another one with entityframeworkcore.

The migrations were working fine before adding EF6 project, but now I can't use the migration's command : add-migration 'anything'

Both Entity Framework Core and Entity Framework 6 are installed. The Entity Framework Core tools are running. Use 'EntityFramework\Add-Migration' for Entity Framework 6.

For the project with EF6 I can add a migration using this way: EntityFramework\Add-Migration 'anthing_here', but I can't add a migrations to the project with EFCore using this way.

Any suggestions ??