Before the 2nd change of MQD rules that made them a lot more humane,
I noticed that Delta bookings are “powered by Expedia”.
I had a short trip to HNL, and I made a test Hertz rental booking via Expedia not Delta). In the checkout process I was able to enter my Hertz membership number.
Test result: my Hertz President Circle status was honored: name on the board and a fun Chevy Camaro SS with a midsize reservation