One of my hobbies is breeding my own zinnias, and I find that it is a lot of fun for several reasons. Zinnia breeding goes much faster than breeding most other plants. Zinnias can bloom in 6 to 8 weeks from seed and the seed germinate in only a few days. They come in a wide variety of colors, flower forms, and plant habits. So there are an almost limitless number of interesting crosses that you can make with zinnias.
They are relatively easy to grow, they grow fast, and they are easy to cross-pollinate. In many places you can get two generations in one year, so you could make your crosses in the Spring, plant "green" seeds from them in the Summer, and see your hybrid blooms in the Fall, hybridize them as you see fit, and save seeds from them before Winter to continue the process the following Spring. Or, if you are impatient to continue without a delay, you could grow those hybrids-of-hybrids seeds indoors under lights or in a greenhouse.
When you are breeding your own zinnias, you can cater to your own personal preferences. I happen to like zinnias whose flowers are rather "open", with petals not packed too closely together. This is an example of a zinnia that I chose as a "breeder" for that reason: