Airborne zombies only make sense in one or two circumstances:

1. A non-zombie enemy maliciously dropping zombies on your head: pilot with barricaded door, and somebody willing to hook troops up to static line then infect them, or who can wrangle zombies into jump rigs without getting bitten themselves

2. A bitten jumper converting to zombie in the plane, and zombifying the rest of the load, followed by a panicked pilot dumping them

Either way, you’d probably get a fair amount of “breakage” in the zombies due to improper body position causing chute malfunctions, poor landings, etc. Personally, I will leave zombie paratroopers out of my planning – I am more concerned about the standard shambling zombie threat.