I'd advise against using a vehicle as a means of holding one end of a zip line.Well,a vehicle with windows,headlights,or panels that could get damaged.
You can use a pully to re-direct the zip-line and have it parked out of the way if possible.remember that the distance the pulley is off the ground will be roughly the distance the zipline will fall when the load is about mid point,plus ofcourse any stretch in the rope.
When it comes to chunks,you might need a "Tail rope",this is usually attached to the block and provides breaking to the chunk on its desent down the zipline,it also is a means of returning the block back to the climber.
Somitimes it is also nesesary to have additional breaking on the zipline,getting a lenght of old fire hose,cutting a hole through it and threadding it on the zipline before you tension it.attach bags of sand/earth to each end of the hose still on the ground and when the pulley hits the hose,it cannot "eat" the hose,ie get stuck in the pulley,so it draggs the bags of sand and takes it to a steady stop.if the bags are to light you can tie previous chunks of wood to the hose also.hanging bags off the zipline can also work for the smaller bits.
I prefer using a tirfor winch to tightnen a steel cable and use blocks that are designed to run on cable,they are generally steel and have "swing cheeks so they can to attached on the cable while its tensioned.
Somtimes hanging a block off a hi ab is a great way,as the peice approaches the truck,the opperator dips the arm and the peice "runs out of steam".
Zip lines can be most efficient in the right circumstances,they can take a long time to set up.I really don't like snatching blocks onto a zipline,it ¨shockloads the system and can cause all sorts of problems.Best have the zipline into a tree or two,or three behind the one you are dismantling if possible.Thats my prefered method,but it dosn't always work that way.