[{"array1":[{item:"value1"},{item:"value2"},],"array2":[{price:10},{price:20},]},]

db.collection.aggregate([{"$project":{array3:{$map:{input:{$zip:{inputs:["$array1","$array2"]}},as:"tuple",in:{item:{"$arrayElemAt":["$$tuple.item",0]},price:{"$arrayElemAt":["$$tuple.price",0]}}}}}},])