This makes it sound that if the destination is in the same zone you do not need to get a different zed

Employee must refund ZED ticket and purchase a new ZED ticket if the following changes occur:

Change to origination and/or destination points are outside of the current ZED– Zone fare they are holding.
Change of itinerary now includes a connection point or change in connection point.

The question I had was SFO and LAX are in different zones but the two zones cost the same. But, the Zone fare is the same.
I will try and call Cathay Pacific tomorrow and also ask the ticket counter when I purchase the ZED.

Thanks
Tony