I have an ear infection that has caused pressure and loss of hearing in one ear. Almost done with zpack and predisone (1 day left). What is next step?

I'd give it time. If you are just finishing your zpac you are early in the recovery process. All purulent otitis media will have transient hearing reduction in the involved ear for up to 2-4 wks. If your symptoms are gradually improving, no action is needed. If the symptoms are unchanged, a revisit with your pcp is in order.
See am ENT doctor. This needs a specialist concentrating on the ears and you should do this asap.