The TRX split squat works mainly your glutes and quads.
TRX Split Squat Form Cue
You’ll step one foot into the strap and turn away from the base point. Make sure to hop or step a few steps forward to give yourself a safe stance to sink down into a squat. (Think of this as lunging with your back leg in the strap.) Make sure as you sink down, you keep a tall posture and watch the front knee to make sure it doesn’t extend past your front toes.