Hi Shaila
MD4C - Multi Level Order Report
It is a report and it will display all the information according to your input. If you pass the Sale Order number in MD4C then it will takes you to MD04 Transaction.
CO41 - Collective Conversion of Planned Order
Here we can convert the Planned Orders to Production Orders by passing the input as Sale Order,MRP Controller or any other input.
we will get the list of Planned Orders and then we can convert it to Production Order in Mass.
If you are looking for MD4C VS CO46 then please go through the below link.
Regards
Suresh.M