Cosmos are relatively easy in the seed starting world of flowers, so yes, similar to zinnias. You can direct sow in the spring, usually in most parts of central Maryland the beginning to middle of April is good. If you have never tried it before you could try to 'winter sow' some in old milk jugs or similar containers, to get a head start on them. You can reference our blog post on winter sowing to read more information on how to try that and there are additional links on the bottom as well. https://marylandgrows.umd.edu/2019/01/23/winter-sowing-how-i-get-a-jump-start-on-my-summer-flower-garden/ The link for the facebook winter sowers group is a great resource because you can refer to what has worked for others depending on region and the type of seeds they have tried. 

You could certainly try to start them indoors but this is depending on your set up and what else you may want to start inside to get a head start. 

Maybe you use some seeds to try winter sowing and save some to start directly in the ground as an experiment to see which succeeds. 

Let us know if you have further questions. 

Emily