You have probably already encountered this after publishing a product to Marktplaats.
'Zip code is too long and should not be longer than 6 characters'
In this case, it refers to the zip code configured in the WooCommerce general settings:
Unfortunately, the space in the zip code also counts as a character and the zip code will be too long, in this case 7 characters. Remove the zip code and try publishing the product again.