You are most likely creating an ulnar deviation which breaks the fulcrum between the hand and arm making it feel weak and awkward. A really bad teacher will tell you to "practice more."
You need to employ several movements. I played that chord but not knowing where you are coming from nor where you are going, I can't give concrete answers. I sort of leaned to the left and brought my arm a little in front of me so as not to twist the wrist.
Of the other movements, if your arm is moving down but then back up the keyboard, you might want to initiate the movement from a little bit of arm weight, a little pronation and a slight forward shift. My thumb was on the outside of the F# and that put my other two far in the black key area where the keys are heaviest. So, you need to find power from someplace else without pressing into the keybed.
"Effortlessness" occurs in the fingers when you use your arm to play. There is no such thing as relaxation at the piano otherwise you'd slip off the keys and fall to the floor.
What gives the illusion of effortlessness is when you use ONLY ONE MUSCLE AT A TIME. For instance, to strike one key with one finger you need only employ your bicep to lift the arm then control the weight or gravity to depress the key. Try it. No use of the finger is needed other than the slightest of flexation to make that one finger a little lower. All the other fingers go down too, which gives the whole hand a relaxed effortless feel. All five fingers can only go on one direction at a time. To use isolation causes two or four muscles to pull on your bones.
One should never use (only) the down muscles to play the piano. All our down muscles are weak because of gravity. You don't need any muscle to go with gravity. Relax all your muscles and you will fall to the floor. See? Effortless.
Your biceps are strong because they battle gravity to lift things up. Your triceps are weak because your biceps lower things to the ground in defiance to gravity. Likewise, your quads are very strong because they lift us up while our hammies are weak because, you guessed it, gravity. Walking down stairs for instance uses your quads in defiance. Each muscle gets to rest while the other is engaged.
Playing the piano is all about up so that your pronators, supinators, bicep, shoulder, elbow, wrist (to some extent) and flexors (to some extent) can do the rest of the work.
Hanon was very close to the answer when he advocated lifting a finger high however, that uses both your extensors and flexors simultaneously and your bones don't know which way to go. This is why many teachers advocate "strength and endurance" however, you are building "strength and endurance" to the wrong muscles and the other muscles don't need it because of . . . gravity. What Hanon didn't know was that isolation created tension and his answer for tension was to relax. RELAX WHAT!?!?!?!?! Well, indeed, relax the muscles you are actually using, the wrong muscles. Replace them with the powerful indefatigable muscles such as the pronator and supinator. Height is the answer but not through isolation. We achieve it through lifting the arm, pronating, supinating, shaping, and above all, never stretching because that employs both the flexors and abductors then you have tension all over again.
So, there is no one answer to your question but, several amalgamated into one.
