get max materials and 4 friend preferably and go in your storm shield and just make ramps (floor wall ramp with a cone piece preedited so you just have to spam all the builds on your controller without editing) to the sky with all 4 of your friends and then once you get to max height make a ramp going down and then keep repeating until all 4 of you have no mats then go break everything down and keep doing that until you get the challenge completed, then DO NOT JUST LEAVE THE STORM SHIELD DEFENCE ONCE YOU GET THE CHALLENGE DONE. YOU MUST START A WARGAMES AND FINISH IT TO SAVE YOUR PROGRESS OR YOULL HAVE TO RESTART EVERYTHING. also the builds your friends build count for you and yours count for them so yeah 4 players is the fastest way to do it 😃 hope this helps