De or het massamarketing?

The correct Dutch article is:

de massamarketing

Rule Words ending in -ing: almost always de. See the rule

How to use massamarketing

the massamarketingde massamarketing
this massamarketingdeze massamarketing
that massamarketingdie massamarketing
our massamarketingonze massamarketing
your massamarketingjouw massamarketing
every massamarketingelke massamarketing
which massamarketing?welke massamarketing?
a big massamarketing / the big massamarketingeen grote massamarketing, de grote massamarketing