Automatically Select/Add Child Taxonomy Terms to post

Hello, thanks in advance for the help.

I have a fairly unique set up using custom post types and custom taxonomies.

Basically I have a Custom Post Type “Companies” and a custom taxonomy “zip codes”

Each company is assigned a zip code and each zip code has services connected with it.

So what I need is to have the child and grandchild terms of the parent term selected to automatically be included.

Example:

Zip Code (selected)
-Service (auto Select)
–Service Brand (auto select)

Thanks again!