Unbound with split VPN and local domain

[Herbert Meier via Unbound-users]

Dear experts,

I would like to configure unbound for my setup but I am totally lost with
the terminology and the settings. Here is my setup:

   - I have a split VPN client runnging that forwards certain subnets to
   the VPN server and forwards *all* DNS request to the VPN server side (I
   guess all subdomains of myvpn.org should be answered by the DNS on the
   VPN server side)
   - I have a local router with domain "lan"
   - I would like to use my ISPs DNS but do caching myself (not sure if the
   router does it)

How could I make all this work, i.e.,

   - Forward all DNS request for *.myvpn.org through VPN
   - Query the route for for request *.lan
   - And use my ISPs DNS (via the router 192.168.178.1) for all other
   queries?

Thanks so much for your help.
Kind regards,
Herbert