Pass a read only interface from one CDT to an interface that uses another CDT

What is best practice for this?

I am trying to make an interface that schedules maintenance for a vehicle  using my maintenance CDT and displays the vehicle information from my vehicle CDT. I am wondering what the steps to do this are. The parent CDT I believe is maintenance as it uses vehicle ID as a foreign key. I already have the read only interface for vehicle information which is uses the following constant to pass information from the vehicles table into the interface. I have also made constants pointing to the data store for maintenance for the process model which I have not designed yet. PLEASE SEE ALL CONTEXT BELOW

I am trying to get the above information to display here:

As far as record types go I have created a new record type for Maintenance and added a related action to my Vehicles record type using:

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