Don't have the necessarly time to write and test a script but i have an idea how to aproach.
It assumes that Cars/Tanks and Choppers are AI controlled.
Solution: 1 CH47D will transport multiple Vehicles from A to B
Fill an array with all vehicles that have to be transported.
Set a LZ where the vehicles has to be set by chopper (gamelogic or invisible H)
Maybe the use of nearestObject [tank1, "CH47D"] might be helpful to see if chopper is close to a vehicle.
As soon the chopper is over a tank and low enough, setpos the tank with a really short loop right under the choppers position.
When arriving at the LZ and as soon chopper has descended to a acceptable flight level, exit the setpos loop, and the tank will be where you wanted.
repeat this for each vehicle or use multiple choppers.
As said, my scripting knowledge isn't good enough to work this out in a acceptable short time, but this would be my approach to this problem.
For sure the scripting heroes in here will point out a few errors in my idea and lead you a better way, but maybe it pushes you in a right direction to investigate