Was inspired by Carnage from Spider-Man? Obviously Zoom as a character predates Carnage, but I don't know when you look at his arc it does seem similar in some ways such as the following.
Both came from abusive homes which shaped their nihilistic philosophy, both even saw their father kill their mother in front of them (though Carnage's origin has changed and sometimes he killed his mother, in one it was his father, with Cletus not defending him.)
Both were raised in an orphanage.
Both became serial killers and were imprisoned after which they gained super powers through a freak accident and became a monster Zoom/Carnage respectively that killed scores of innocent people.
In both cases they gather a team of similar freaks, monsters and psychopaths together as a family that terrorises the city and turns it into a no man's land for a while (metappocalypse/Maximum Carnage.)
In both cases their right hand woman is a psycho who has sonic powers (Shriek/Black Siren.)
The heroes archenemy has to team up with the hero to stop them. (Venom in Carnage's, whilst in the Flash's it's a bit more complicated as it's technically not Thawne, but an alternate version of the man whose face he stole, but it is the same actor and so the viewer has to basically see the previous villain team up with the hero to stop the current one. In both cases the previous villain was an evil version of the hero, whilst this one is an evil, EVIL version of the hero.)
There are also parallels with Zoom and Spider-Carnage too, in that both are monstrous versions of the hero from another universe that overruns its home city and then creates a super weapon to destroy all universes.
Possibly a coincidence, but maybe not?
Both came from abusive homes which shaped their nihilistic philosophy, both even saw their father kill their mother in front of them (though Carnage's origin has changed and sometimes he killed his mother, in one it was his father, with Cletus not defending him.)
Both were raised in an orphanage.
Both became serial killers and were imprisoned after which they gained super powers through a freak accident and became a monster Zoom/Carnage respectively that killed scores of innocent people.
In both cases they gather a team of similar freaks, monsters and psychopaths together as a family that terrorises the city and turns it into a no man's land for a while (metappocalypse/Maximum Carnage.)
In both cases their right hand woman is a psycho who has sonic powers (Shriek/Black Siren.)
The heroes archenemy has to team up with the hero to stop them. (Venom in Carnage's, whilst in the Flash's it's a bit more complicated as it's technically not Thawne, but an alternate version of the man whose face he stole, but it is the same actor and so the viewer has to basically see the previous villain team up with the hero to stop the current one. In both cases the previous villain was an evil version of the hero, whilst this one is an evil, EVIL version of the hero.)
There are also parallels with Zoom and Spider-Carnage too, in that both are monstrous versions of the hero from another universe that overruns its home city and then creates a super weapon to destroy all universes.
Possibly a coincidence, but maybe not?
