How well did Hitler incorporate the productive resources of the conquered nations into the Third Reich's war effort?

During World War II, the Nazi regime did a great deal to
exploit the resources of the countries that they counquered.  One might argue that they
could have incorporated those countries' resources more efficiently, but it is clear
that the Germans tried hard to extract productive resources from the countries they
conquered.

The most obvious way in which the Nazis did this
was through the use of slave labor or, at least, of coerced labor.  Over the course of
the war, Germany forced millions of people from conquered countries to come to Germany
to work.  The link below shows us that, by 1944, there were 7 million people from
foreign countries working in Germany.  Essentially none of these people were free
workers.  In this way, Germany tried to take the labor force of many of the occupied
countries and use those resources for German ends.

The
Nazis also did a relatively systematic looting of the conquered areas.  Large amounts of
machinery, among many other items, were simply taken from the conquered lands and
brought back to Germany.  This represented another attempt to incorporate those
countries' resources into the German war effort.

It is
possible that the conquered nations would have been more cooperative if Germany had been
less brutal in its exploitation.  This might have made Germany better able to
incorporate their economies into its own.  Be that as it may, Germany clearly tried hard
to exploit the resources of the conquered countries.