I find that the Zora anatomy can be a bit difficult to draw so I made this guide but why keep it to myself.
This is for your basic male Zora I might upload a female Zora guide later. The blue lines are your basic body while the green lines are guides for things like fins, tails and gills. The top image is coloured to help distinguish the top scales from the underbelly.
The green lines are probably the easiest thing to modify to give your Zora oc a unique look. Colour is a great way to set your oc apart. It can be something as simple as a gradient effect blending the tops scales and underbelly, or you could go wild with markings.
I hope this helps anyone looking to make their own Zora oc. Now get out there and flood the ocean with your creations.