Nick Seafort wrote:
...what truck? I certainly never saw it

And it may have been confounded by Zeus having repaired/refuelled the vehicle manually when it became apparent that it had an empty tank - this would have moved locality to him afaik (and possibly even created a new vehicle ID), and depending how the objective is coded may have stopped it firing.
It's very unlikely Zeus can break the trigger. To complete the mission you just need to get the damaged vehicle back to within 5 meters of the repair base. The script maintains the ID of the vehicle, which Zeus cannot change.
During testing I even completed the mission by dragging the vehicle back via Zeus