edirectory 8.6 mixed with ds 6.21

i have a netware 6.5sp8-tree with edir 8.7.3 running. to service an old
DOS-application for VLM-clients we have one netware 4.2sp9 with ds 6.21
which holds no replicas.
now we plan to install a new IDM 3.61 server which needs minimm
edirectory 8.8.5.

can i mix this with ds 6.21 ?