[{cards:[{id:"56456",name:"paul",contacts:[{id:"1",text:"first contact"},{id:"1",text:"second contact"}]},{id:"56456",name:"john",contacts:[{id:"1",text:"first contact"},{id:"1",text:"second contact"}]},]}]

db.collection.aggregate([{$unwind:"$cards"},{$unwind:"$cards.contacts"},{$addFields:{name:"$cards.name",text:"$cards.contacts.text",}},{$project:{"name":1,"text":1,"_id":0}}])