Universal Containers sells a subscription Product Z that is sold in yearly segments, but would...

Write a Price Rule to run when Product Code = Product Z and Segment Index = 1, with a Price Action setting Non Discountable to True.

Set First Segment Term Editable to Only Custom Segments in the yearly Price Dimension record.

Create two Price Dimensions, then set Non Discountable to False on the first Price Dimension.

Write a Price Rule to inject 0 into Additional Discount when Product Code = Product Z and Initial Segment = True.