Hibiki stats: Non Mega, Mega adds an Extra 100 into each stat though will cause effects such as Fatigue, Injurys to itself or partner if the mega form is prolonged. Stats calculated using Lopunny and Mewtwo Maxed stats, also looking at Lopunny maxed Stats and Mewtwo lowest stats if needed to make her less overpowered but still significantly more powerful then an average pokemon.

HP: 750
Attack: 626
Defence: 599
Sp Attack: 674-100 due to nature being Adament/Jolly
Sp Defence: 626
Speed: 733 based on a Jolly nature. -100 if Adament natured

Zerina stats: Same rules as Above.

HP: 740
Attack: 689-100 due to Timid/Modest nature
Defence: 546
Sp Attak: 819 if Modest. -100 if Timid
Sp Defence: 546
Speed: 733 based on a Timid Nature. -100 if Modest.

So this is my calculation by adding up the maxed Stats of Mewtwo and Lopunny/Zoroark. As you can see, Hibiki is uber powerful like Zelina only difference being Hibiki will hurt herself when she goes Mega for longer then let's say 10 to 25 minutes?