The 30 second ad was cute. You have a sense of what plays well. Work up to the longer features by writing a few more shorts (3-10 pages). Get some feedback, polish them, then see if you're videographer can help you film them with the help of a few friends. Once you've built up some experience, tackle the zombie picture.
Or alternately, write up a couple of your zombie scene ideas and film them. They don't tell the story but you will get some immediate gratification and also see what works--scriptwise and visually. It's kind of a live action storyboard.
I believe there's an Indiana Horror Film Festival. You might check about entry requirements. It's a good way to find out techniques and network. Usually festivals draw in people from surrounding states, so you may find a budding director/writer equally interested in finding a partner near you.
Don't give up. But certainly don't wait for someone else to do the writing!
