How can I treat these malar mounds/festoons that I developed after getting under eye filler (Restylane Lyft). Need help! (Photo)

Don’t make things worse with bad treatments. If you have had 6 rounds of enzyme, it means the doctor treating you does not know what they are doing. A single massive dose of hyaluronidase (300 units) is what is needed. It is likely you simply have not gotten enough enzyme.

More than likely, if an appropriate amount of hyaluronidase is injected into the area of the filler / mounds you will see things normalize. Hyaluronidase works very quickly, within a day or two, but any swelling can take a few weeks resolve so be patient.Andrew Campbell, M.D.Facial Rejuvenation SpecialistQuintessa

It does not surprise me you have festoons after 6 treatments with hyaluronic acid fillers for your lower lids...since the mechanism of action of the hyaluronic acid fillers is that of a sponge....they take on water and swell.  Then they get resorbed.  This back-and-forth cycle of swelling and deflation can actually reduce the tight coiling of healthy collagen/elastin.  So repeated injections of those fillers in the same area can lead to laxity in the skin.
I recommend having a biostimulatory agent (Sculptra, BellaFill, or Radiesse) injected into the lower lid area, as it will trigger 2 kinds of collagen synthesis, including a stiffer one to fill in the hollow, and a softer one to improve skin texture, including improved dermis thickness.  Additionally, a skin-tightening procedure done about 2 weeks to 2 months over the top of the (biostimulatory agent treated) area will augment results. Skin-tightening procedures would include things like microneedling, microneedling with radiofrequency (such as Pixel8-RF or Morpheus8), a medium-depth chemical peel, Vampire facial (microneedling with Platelet Rich Plasma), Ultherapy, and certain lasers.  Another recommendation it to take Vitamin C  (at least 1000mg daily) for about 4 months after the injection to optimize collagen synthesis (since vitamin C is a co-factor for collagen synthesis).  Yet other things that can increase the tightness of skin include Celluma medical-grade LED light therapy, and using medical-grade skin care (retinoids, human stem cell growth factors, and micro-technology products).

If this condition was not present before filler then it should slowly return to the way it was prior to treatment once all filler is dissolved.  If it was present prior you can consider lasers or FaceTite with Morpheus8 treatments to help improve the area.

Eyelid skin is 1/7th as thick as cheek skin.Amuch thinner filler such as Silk or Volbella is better to use. The proper dose for hyaluronidase is somewhere around 30 U for each 1/4 cc of filler used.Juvederm Ultra requires a little more in my opinion

There is always a risk of swelling, bags, and pseudo-festoons after hyaluronic acid fillers under your eyes. This class of fillers attracts and retains water and it may act differently in each person making fillers under the eyes less predictable. If you did not have bags or festoon before the filler then the anatomy should return to normal over time provided the filler has been dissolved with hyaluronidase. I would recommend a low salt diet, gentle lymphatic massage over the swollen area 4 to 6 times each day, and waiting at least two weeks before repeating the hyaluronidase. Hyaluronidase itself can cause swelling and loosening of soft tissue so you don't want to overdue this agent. We generally wait at least two weeks between hyaluronidase injections to avoid overdoing this agent which can have negative consequences.