update tb_item_estq set 
    vl_estq = 0
where
    not exists (select 1
                from tb_invt_item
                join tb_invt on
                    (tb_invt_item.id_emp = tb_invt.id_emp and
                     tb_invt_item.id_invt = tb_invt.id_invt)
                where
                    tb_item_estq.id_item = tb_invt_item.id_item and
                    tb_item_estq.id_emp = tb_invt_item.id_emp and
                    tb_item_estq.id_dep = tb_invt.id_dep and
                    tb_item_estq.id_grd_estq = tb_invt_item.id_grd_estq)