Peter You can only have 1 business account in 1 pack. So if you want two business accounts you'd have to join (or create) two packs.
I think some (most?) "ZZP-ers" use their personal account for their business. Because you can have 25 bank accounts you can separate the money flow. However a Personal account will be in your own name and not something like "Klusbedrijf Jansen" or "Adviesbureau De gele Aardappel". If you want a name like this you have to have a Business account where that name is registered at the Chamber of Commerce.