Hello Michel,
If you could get a range table for the second internal table, then you can use the below delete statement.
delete itab_1 where <field> not in range_tab.
In case of comparisons of more than 1 field,
delete itab_1 where <field1> [not] in range_tab1
[AND] [OR] <field2> [not] in range_tab2 and so on.
Regards,