Database
db={"col1":[{fieldX:"x",fieldY:"y",date:"2022-01-15 12:00",condition:{enabled:true,condition:"abc",}}],"col2":[{fieldZ:"z",date:"2022-01-15 15:25",condition:{enabled:false,condition:"bce",}}]}
Query
db.col1.aggregate([{$project:{date:1,_id:0}},{$unionWith:{coll:"col2",pipeline:[{$project:{date:1,_id:0}}]}},{$sort:{date:-1}},{$limit:10}])