Are they licensed professionals or are they just plant enthusiasts that attempt to create new species of plants as a hobby?
What exactly are hybridizers?
Anyone who is interested in cross-pollinating plants, or who actually does it, is a hybridizer with respect to this forum. No license or professionalism is required.
I am an amateur zinnia breeder -- underline the amateur -- and hybridizing by cross-pollinating is one of the ways that I get some interesting new zinnias. I think it is kind of fun to cross various zinnias with each other to see what the results will be. Zinnias come in a great variety of colors, flower forms, and plant habits, and the number of possible crosses that are possible with zinnias is mind boggling.
Crossing zinnias is easy to do, and fun. There is a special excitement waiting for a new hybrid zinnia of your own making to open its first bloom, to see what surprises are possible. I never tire of that suspense. Some zinnias can have a very "un-zinnia-like" look.