Hello Piet,
In Zeebrugge there are not much interesting spots for photographing.
It's all secured area but around the inner harbour (fish market) and the entrance of the Van Damme lock are good places.
Also at quay 408 where the URS tugs are it's not bad but only in the afternoon, this due to the sun.
You also have the opportunity of the southern breakwater but your not allowed there by car as far as I know so unless you have a cycle it's a long walk on foot.
cheers
Leon