De or het marktordening?

The correct Dutch article is:

de marktordening

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

How to use marktordening

the marktordeningde marktordening
this marktordeningdeze marktordening
that marktordeningdie marktordening
our marktordeningonze marktordening
your marktordeningjouw marktordening
every marktordeningelke marktordening
which marktordening?welke marktordening?
a big marktordening / the big marktordeningeen grote marktordening, de grote marktordening