seriously...... 5000 calories a day from SOLID foods... 
I hit 3600 in solid food without even trying, and thats adding mushrooms green beans peppers etc to bulk the meals out even more.
No fast food, desserts, fizzy drinks, just whole sources of carbs and protein cooked from fresh
I could eat 5000 easily and comfortably
whether zack eats 4500 or even tracks it all (which i doubt) is irrelevant, if you're not putting weight on then YOU need to.