The hips require flexibility, strength and great movement. There are so many disciplines to improve your hips and it’s a very important area to improve and maintain as the hips are the hub of your power and the foundation to your physical health.
For flexibility, yoga and martial arts are amazing because a lot of hip improvement comes from groin flexibility so moves that are encompassed within these disciplines, e.g. stretches or progressions to the box and side splits, are excellent
For movement, the dynamic movement parts of tai chi, boxing and Thai boxing and oblique core drills get you strong at the rotation and opening of the hip.
And for stability and strength, Olympic lifts and squat and deadlifts are foundations to the strength of the hip.
Combine these practices for healthy hips and you will have a healthy life. Joseph Pilates had a saying that you are as young as your spine and he believed you kept youthful from the health of your spine. I believe the hips hold as much power, and you are only as powerful as your hips.