[{"_id":1,"field1":[1,2,3,4,5],"field2":["a","b","c","d","e"],}]

db.collection.aggregate({"$unwind":{path:"$field1",includeArrayIndex:"field1_index"}},{"$unwind":{"path":"$field2","includeArrayIndex":"field2_index"}},{"$project":{"fields":{"field1":"$field1","field2":"$field2"},"diff":{$cmp:["$field1_index","$field2_index"]}}},{"$match":{"diff":0}},{$group:{_id:"$_id",fields:{$push:"$fields"}}})