How can I erase all non-locked cells in a protected worksheet with one keystroke

RLevkoy 

Since there can be many ways to find a solution, allow me to show you two of these ways

A. without VBA the following workaround may be feasible:
1. Mark all unlocked cells while holding down the CTRL key so that all are marked
2. Give this cell range a name, the easiest way is to enter the name in the address field (top left next to the editing line).
3. Now you can select all these cells at once at any time by selecting this name in the address field again (drop-down!)
4. Now you can delete all cells with one click.

B. with VBA

Delete sub ()
Dim z As Range, sh As Worksheet
choice = MsgBox ("Do you really want to empty all unprotected cells in all sheets," _
& vbCrLf & vbCrLf & "AND" _
& vbCrLf & vbCrLf & "delete all current data?", vbYesNo, Title: = "_
Set everything to zero ")
If choice = vbYes Then
For Each sh In ActiveWorkbook.Worksheets
For Each z In sh.UsedRange
If z.MergeArea.Locked = False Then z.MergeArea.ClearContents
Next z
Next sh
MsgBox "Your data has been deleted!",, Title: = "All sheets are now at zero _
posed !"
Else: MsgBox "Your data was not deleted!",, Title: = "No new year _
started! "
End If
End Sub

'Formulas translation from German