"Arthur works even less quickly than you."
Translation:Arthur travaille encore moins vite que toi.
As far as I know, "meme" is used as "the same" or to signify some sort of equality. As a result, it would seem out of place in a comparative sentence. "Encore," however, refers to the "even [more/less]" part of this sentence. Maybe it would help if I put it this way: try substituting "the same" in for "meme" and you will hear the contrast more clearly. For any of you native French speakers out there, please feel free to correct me if I'm wrong! I hope this helps!