To bootstrap a DU4 non-global zone you need to edit /etc/apt/sourses.list and copy sources below (do not forget to make the backup of original sourses.list of global zone: sudo cp /etc/apt/sourses.list /etc/apt/sourses.list.orig):
deb http://10.20.60.188/dilos4 du4-unstable main contrib non-freedeb https://apt2.dilos.org/dilos du3-unstable main contrib non-freedeb https://apt2.dilos.org/dilos dg2-unstable main contrib non-free#deb-src http://10.20.60.188/dilos4 du4-unstable main contrib non-free
Install a zone using regular commands (zonecfg, zoneadm).
Do not forget to revert the changes in the sources.list file when a non-global zone has been installed (sudo cp /etc/apt/sourses.list.orig /etc/apt/sourses.list).
The last line shall be uncomment if zone planned to be used as build one to have an access to source-packages.