De or het smokkelzaak?

The correct Dutch article is:

de smokkelzaak

How to use smokkelzaak

the smokkelzaakde smokkelzaak
this smokkelzaakdeze smokkelzaak
that smokkelzaakdie smokkelzaak
our smokkelzaakonze smokkelzaak
your smokkelzaakjouw smokkelzaak
every smokkelzaakelke smokkelzaak
which smokkelzaak?welke smokkelzaak?
a big smokkelzaak / the big smokkelzaakeen grote smokkelzaak, de grote smokkelzaak

Dutch words ending in smokkelzaak

mensensmokkelzaak

In compound words, the last part decides the article. See the rule