Odds are that most of the damage is on the outer surface which is fairly easy to deal with and may be enough. You have to be careful to avoid all lettering on the inside. Years ago I bought two Meguiar's products and have had very good luck doing exactly what you are wanting to do. The products are M17 Plastic Cleaner and M10 Plastic Polish. The cleaner is used first, followed by the polish. I place the lens lettering down on top of a soft towel and apply it to a soft cloth and thoroughly "buff" the face of the lens. That should remove most moderate damage. I follow that with a similar application of the polish. If the backside still looks like it needs work the same process can be use. Just avoid the lettering.
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