I have a custom object 'X', while creating a new record in object 'X' there a lookup field related to account object, when i select any account name 'Vinay' then the 'vinay' related account record field should be auto-filled in the 'X' object like email,phone,billingCity? how to achieve this?
If you do want to edit those field values then You can use Formula fields and use the formula like below
if You want to edit these fields after saving the record then Go For Process Builder OR workflow to update the Field values in Object X from Account. To update the fields formula will be same as above
The criteria for Process Builder will be Account Not Null
Note: - Use the Correct API name and Use Insert Field option to Select the Field