Secondary DNS info at this post: Vanity nameserver with secondary dns hosting - #7 by mylo
With the config in MIAB set to:
ns3.box.domain.pro ns4.box.domain.pro ns5.box.domain.pro xfr:88.198.106.11 xfr:185.136.176.247 xfr:103.6.87.125 xfr:108.61.224.67 xfr:173.244.206.26