how can I get my new HP OfficeJet 9025 to print and scan from my OS X El Capitan equipped Macbook Pro

You may be able to use AirPrint with your older Mac OS X 10.11.6; & other options may exist.

• HP Printers - macOS and OS X Compatible Printers | HP® Customer Support

https://support.hp.com/us-en/document/c01664444

Examples and details in this article could be helpful. My printers are wired/wireless.

Go to Printing with Apple AirPrint (Mac) to use Apple's built-in printing solution.

So this should be workable. The correct drivers should work; &/or AirPrint could, too.

Most HP printers work with Apple AirPrint

This all-in-one printer software page shows El Capitan 10.11.6 "full-drivers" are available :

• HP OfficeJet Pro 9025 All-in-One Printer Software and Driver Downloads | HP® Customer Support

https://support.hp.com/id-en/drivers/selfservice/hp-officejet-pro-9020-all-in-one-printer-series/23918456/model/23918457

Good luck & happy trails!🌻🌤