Of course you didn't explain what leg exercises you are doing now. Achilles rupture (tear/snap?) is pretty serious stuff, with the stretch and flexibility factor part of the recovery problem. During rehabs I'm sure you used different resistance type machine to strengthen the whole muscle chain, from the hips down to the toes.
Don't know if your using machines or not, but If doing BB squats than do them with the heels raised on a 2X4 or a couple of 45 plates. Less stress on the Achilles and more focus on the tear drop affect/quads. Front squats are excellent this way. As are BB Hack squats.
Really no logical reason to do hams on a different day than quads. With total leg training, using a higher rep scheme, with perhaps more SS's, tri or quad sets may boost up results pretty fast. Lighter weight and more pump may be what your after.
Wonder if training calves is a problem with you. The stretch and coming up on the toes may need an adjustment after Achilles surgery. Good Luck.