We enjoyed both Horizons and Petit Pariz. Both are for Zilara guests only, although Petit Pariz is on the Ziva side (which led to some entertaining exchanges when Ziva guests were turned away).
If I was only having one dinner, I'd choose Horizons. Its open-air setting on the beach is very nice and the cuisine is a little more "local". My only caution might be the evening temperature in August. It was absolutely delightful in mid-March, but I don't know if it would cool down enough in the summer.
Petit Pariz was also very good, but the menu could have been found in any reasonable "French" restaurant around the world. Petit Pariz did have some issues with its attempt to be a little more "formal". It has a dress code for men, requiring a shirt with collar, long pants and closed shoes. The guests did comply, but some with torn jeans, well worn polo shirts and beat up tennis shoes. An interesting contrast to others who were in business attire ...
We also liked the bar in the Zilara lobby (Potionz ?). We had a night cap there every night of our stay and it was never very crowded - maybe one or two other couples. They seemed to have the largest selection of liquor, including some aged Jamaican rums that were fun to taste. The atmosphere was more casual the the "old men's club" feel of the former Ritz bar near the Ziva lobby.