[{_id:1,"_a":[{"_p":[{_pubId:{"CC":"EN"},_prid:"2",s:{c:{text:[{secId:"4"},{secId:"5"}]},d:{text:[{secId:"6"},{secId:"7"}]}}},{_pubId:{"CC":"CZ"},_prid:"4",s:{c:{text:[{secId:"8"},{secId:"9"}]}}}]},{"_p":[{_pubId:{"CC":"CZ"},_prid:"200",s:{c:{text:[{secId:"4"},{secId:"5"}]},d:{text:[{secId:"6"},{secId:"7"}]}}},{_pubId:{"CC":"BG"},_prid:"4",s:{c:{text:[{secId:"8"},{secId:"9"}]}}}]}]}]

db.collection.aggregate([{$match:{"_a._p._pubId.CC":"EN"}},{$unwind:"$_a"},{$match:{"_a._p._pubId.CC":"EN"}},{"$addFields":{"_a":{"$filter":{"input":"$_a._p","as":"x","cond":{"$eq":["$$x._pubId.CC","EN"]}}}}},{$unwind:"$_a"}])