How to get a flat stomach and thick thighs/butt together?

Okay so this journey is so hard for me. I do exercises for both, but it seems each need opposite things. For instance, to maintain thick muscular legs you need to eat more calories but for stomach you need to eat less calories. I am also trying to gain weight in general in my arms and legs so do workouts to make sure I get more muscle than fat. When I try to gain weight, most of it goes to my stomach. How do I gain weight, get thicker thighs and maintain a flat stomach simultaneously? It seems impossible. Please help, I just want to achieve my goals. Ab workout are just not working and my legs are staying skinny...