[5] Zarazúa made her WTA Tour singles debut at the 2016 Brasil Cup, after she reached the main draw through qualifying, but to lost in the first round Catalina Pella in three sets.

[8] In February, Zarazúa received a wildcard to play at the Mexican Open in Acapulco, where she reached her first WTA Tour singles semifinal with wins over top seed Sloane Stephens,[9][10] Katie Volynets[11] and Tamara Zidanšek,[12][13] before losing to Leylah Fernandez.

[15] She defeated wildcard Elsa Jacquemot recording her first Grand Slam win,[16] and becoming the first Mexican woman to do so since Angélica Gavaldón reached the second round of the 2000 Australian Open.

[24] In February, playing with Iryna Shymanovich, she won her first WTA 125 doubles title on home soil at the Puerto Vallarta Open, defeating Angelica Moratelli and Camilla Rosatello in the final.

[31] Partnering Angelica Moratelli, she was runner-up in the doubles at the WTA 125 Bari Open, losing in the final to top seeds Anna Danilina and Irina Khromacheva.

[32] The following week, Zarazúa and Moratelli reached the final at the WTA 125 Valencia Open, but again suffered defeat, this time to second seeds Katarzyna Piter and Fanny Stollár in a match which went to a deciding champions tiebreak.

[42] As the top seed at her home tournament, the Mérida Open, she made the quarterfinals defeating wildcard Akasha Urhobo[43] and qualifier Maja Chwalińska,[44][45] before losing to eventual champion Zeynep Sönmez.

[47] As the top seed at the Fifth Third Charleston in November, Zarazúa won her second WTA 125 singles title, defeating Alina Charaeva,[48] Irene Burillo Escorihuela,[49] Louisa Chirico[50] and Lauren Davis[51] to reach the final, where she overcame Hanna Chang in straight sets.

[55] Only main-draw results in WTA Tour, Grand Slam tournaments, Fed Cup/Billie Jean King Cup and Olympic Games are included in win–loss records.