Be sure to bring along A LOT of overlords because they will be instantly targeted. Pound for pound, mutas work pretty well here, but don't forget to expand. Expand as much as you can. This is a necessity. Marine and Medic Drop- this kind of drop can be stopped very easily by the zerg.
Lurkers are the key.
I like to put one or two lurkers right in the middle of my drone line to bring an abrupt end to any drop on my drones. A couple of lurkers at the perimeter of your base are a good idea as well. And of course, be sure to counter attack if you utterly destroy his force with minimal loses to your own troops. When someone drops, they usually drop with everything they've got. Be sure to take advantage of this weakness.