UCS Director is focused on Infrastructure automation while CloudCenter is on App layer.
Both has integration with ACI and hence you can see some overlaps. CloudCenter will automate all the ACI constructs that are required for App deployment.
UCS Director will automate right from Physical/Virtual domain on-boarding, UCS configuration, vCenter configuration, Tenant creation and much more.
Please refer the below document on UCS Director which provides all the ACI tasks that it provides you to automate out of the box.
UCS Director: Login as Admin --> Orchestration (or Policies --> Orchestration) --> Workflows Tab --> Click on 'Task Library' and look for 'Cisco APIC Tasks'. There are around 240+ tasks that you can automate APIC operations in UCS Director.