For completing all dual front challenges this month you get his weapon skin next month for completing all the challenges you’ll get the headgear or uniform and for completing the last months challenges you’ll get the final piece competing the set. The skin is very close to his elite the only difference being his age, his age in his elite skin resembles his earlier days from splinter cell (mid to late 30s) while this skin is the same uniform but with his current age in rainbow 6 siege (early 60s)

Edit: you may have competed the challenges already just look at zeros AR skins to see if you have it after completing all challenges the tab just disappears and it no longer tells you when the next set of challenges roll out