As others have reported, taking the day off after legs as a scheduled rest day helps. Even a 15 minute 'power nap' aids in recovery. I have also experimented with higher calorie intake pre/during/post leg day, it only made the tired lethargic feeling worse as my body struggled to adjust to the sudden strain on my digestive process.
I never exceed 40 minutes in the gym and take a kitchen sink of powders before and drink it before and during plus plenty of water. Immediately after the workout I slam a small hand full of skittles. Chew on them and savor the sugar then swallow more water. On the way home I drink pasteurized egg whites mixed with Liquid yogurt from a chilled hydroflask then eat a tiny oat bite from Bobo. It saves me from tearing my wife's head off verbally when I get home cause I would be starving and doesn't rob bloodflow with complex foods for digestion.
For some reason it doesn't make me any more tired than any other day in the gym and I train my legs hard as hell. I will do rest pause, drop sets, widow makers, etc... for the major movements like, squats, leg press, hack squats, etc...
I do eat about an hour before I go to the gym then I will eat a homemade protein bar with an intraworkout EEA/creatine mix in the middle of my workout. I also eat about an hour after I finish the gym. This probably helps.