Do you speak Dutch already? I am assuming you don't otherwise you would know why you have looked on a website for Dutch schools in Brussels. That website is exactly for what it says it is, for enrolments for BRUSSELS.
Zaventem is not in Brussels. All Zaventem schools do their own enrolments, as per what you can read on their websites. Enrolment dates vary.
Now if I am right in assuming you cannot speak Dutch, then I would say to think very very very hard about school choices because the majority of Dutch speaking schools will refuse to speak to you if you don't speak to them in Dutch. In French schools and the minority of Dutch schools, no such rule and makes communication far easier.
Don't be choosing Dutch on the false assumption their schools are better, the PISA results indicate that comparing like for like Dutch and French schools, the biggest determining factor on performance is socio-economic group, not language.
Dutch schools do not offer English!!!!!!!!!!! Not until secondary age 12. And in Brussels Dutch schools cannot offer English until age 14. The only exceptions are a tiny few who have opted into the new immersion system and it is only a few hours a week and NOT for English speaking first language.
If you are after local public Dutch schools offering English, well I'm afraid you won't find any. There are a few French schools, outside of Brussels, 25km south of Brussels, which offer English immersion - NOT for English speakers, plus the ONLY public school in Belgium in French system which offers English to mother tongue speakers called Le Verseau. You have to pay 5k. Living in Zaventem and going to Le Verseau will mean having to have a car just to make this commute and you'll spent 2 X 2 X 5 = 20 hours a week in the car.
If you want a school teaching in English below the age of 12, then you will have to go for the private system and will pay a minimum of around 10k up to 30k.
Now is there a specific reason why you MUST live in Zaventem?
If there is no specific reason why you must live in Zaventem, then do widen your area search and that would mean considering French schools too.