The Dutchman has now scored 17 goals this season and has racked up 33 goals in 30 games for the calendar year.
Wenger said: "He is in a period where he doesn't have to look for goals. They just come naturally for him, he is always in the right place at the right moment.
"He got two goals tonight from positions where it looks easy but that's only because he understands the game so well.
"At the moment Robin is an exceptional player. He takes advantage of our offensive style. At the moment he is the one who scores all the goals so we hope we can keep him fit and with us for a long time."