How to counter Zeri
Let us take a look on how to beat Zeri. We will look at champions who are strong against Zeri and who are weak against Zeri. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Adc champion who counters Zeri. You can already win in champion select with the right counters for Zeri. If you want to know how to counter Zeri then you need to take into account the best picks vs Zeri and the worst picks vs Zeri. This Zeri counter data is based on matches played by Pros on patch 15.11 and previous ones. It is important to see whether Pros counter picked Zeri or whether they played as Zeri.
Champions used by Pros to counter pick Zeri
Looking at the matches from Pros (see table Pros counter picked Zeri) we can see that they picked 
Ezreal most often to counter pick Zeri. The matchup Ezreal vs Zeri occured 33 times. Zeri has 17 wins and 16 losses in this matchup. Learn how to counter pick Ezreal to get another perspective on the data.
Lane outcome for Zeri
When looking at Zeri counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Zeri. The lane outcome of Zeri consists of three outcomes: Win, Loss or Draw. Let's take a look of Zeri lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Zeri.
Conclusion
Analyze the available data and learn how to beat Zeri. To master Zeri take also a look on Zeri builds and runes for Zeri. Good luck, Summoner!