I've done it. Another website used to do a 4 park challange making use of WDW transportation and requiring 3 attractions in each park.
Animal Kingdom was my starting point. I rode the bus from PO-FQ for early entry. Did Dinosaur, Everest, and Bug's Life. before leaving. This was done in FP era, so I got three for the second park. Rode the bus from AK to DHS. This was the longest I had to wait, although I met a nice DISer at the bus stop that was doing something similar. Went to DHS and rode Tower of Terror, R and R Coaster, and Star Tours. Replenished FPs after each check in for Epcot. Rode boats from DHS to Epcot's International Gateway (today you could also take the Skyliner). Walked around World Showcase eating at a couple of Food and Wine food booths before eating a favorite ham, apple, and cheese sandwich at the fast food place in Norway (sadly never re-opened after COVID). Rode Mexico boat ride, Soarin' and Spaceship Earth. Checked on MK FPs after each entry. Rode the monorail from the front of Epcot to the TTC then switched over to the MK monorail. Rode PeopleMover, Under the Sea and finished up on Pirates. Finished up around 4-5 ish.
I am an early riser and was able to get on one of the first busses to the AK in the morning. Although the day went smoothly, I was surpringly worn out around 2-3 o'clock. Probably because of adrenaline rush in the morning. It was a very fun experience.