How do you suggest I make this cake?

I want to make a normal nine inch round three layer cake, and i want each layer to be different, i want the bottom one to be a neon rainbow, then i'll put one the frosting, and then i want on top of that a zebra cake, then i apply more frosting liberally, and then i want on top of that a regular red orange yellow green blue and violet cake, then i frost on top of that, and then the sides. But the problem is that I don't know how to make only one layer of each, i mean i know how to do it, but i need the exact measurements, cause i can make a nine inch two layer zebra cake, i can make a two layer nine inch rainbow cake, and i've made a neon cake, but how do i do all three?