It sort of depends on how fatigued you are as well. When I'm in shape, doing 3-4 hours of z2 shouldn't ruin the rest of my day, if I'm well fueled and rested. But doing 6+, yeah, I can typically count on being brain dead.
It also kind of depends on what types of things that you wanted to do with the rest of your day. Doing things like laundry, cooking dinner and straightening up the place are easy, important (essential) and don't require too much energy IMO. Neither should socializing or spending time with friends.
Studying for something? Working? Practicing a difficult classical piece on the piano? Yeah, maybe I'd do that before the ride, or on the other weekend day.
__________________
"Your beauty is an aeroplane;
so high, my heart cannot bear the strain." -A.C. Jobim, Triste