Could you please tell me what kind of insects go after zinnias?, Some of my plants are drying up and going brown.

Zinnia as a species is more prone to diseases such as powdery mildew, grey mold or leaf spotting, than to insect-related problems. Check the plants carefully. "Defender", from "Safers", is a good control for most types of plant problems. If insects are the problem, "Safer's Insecticidal Soap" will control most types of pests.