how to optimize vba looping code using variables?

• first off: avoid Select/Selection/Activate/ActiveXXX pattern and use fully qualified range references.

  this will lead to a better control over what ranges you're actually acting on and best performances without all that sheets jumping

  so since you're using "looping table" sheet for filtering criteria values reading purposes while the hard work is done in "looping" sheet you may want to act like follows

  With Sheets("looping table") '<--| reference "looping table" worksheet
      'your code to gather filter criteria values
  End With
  
  With Sheets("looping") '<--| reference "looping" worksheet
      'your code to do the filtering and writing
  End With
  

• all those es variables filled with the content of cells on the same row call for arrays

  reading values from cell into an array and then use this latter for those values retrieval is a much better performing action

  like:

  Dim eFilters As Variant, eVals As Variant
  
  With Sheets("looping table") '<--| reference "looping table" worksheet
      eFilters = .Range("O3", .cells(.Rows.Count, "I").End(xlUp)).Value '<--| store its columns "I" to "O" values from row 3 down to column "I" last not empty one
      eVals = .Range("P3:Q" & .cells(.Rows.Count, "I").End(xlUp).Row).Value '<--| store its columns "P" to "Q" values from row 3 down to column "I" last not empty one
  End With
  

• once you have those arrays you can nest two loops:

  • outer loop to go through their rows as if you were looping through "looping table" ones

    to this purpose the Application.Index() method comes very handy, where you can strip off a single row out of an array by typing:

    Application.Index(myArray,iRow,0) '<--| this references the iRowth row of myArray array

    so that

    Application.Index(myArray,iRow,0)(iCol)

    references myArray elementh in iRow row and iCol column

  • inner loop to AutoFilter each "looping" sheet column with corresponding Criteria

    so that all that:

     .AutoFilter Field:=1, Criteria1:=ee
     .AutoFilter Field:=2, Criteria1:=ex
     .AutoFilter Field:=3, Criteria1:=ez
     .AutoFilter Field:=4, Criteria1:=es
     .AutoFilter Field:=5, Criteria1:=ef 
     .AutoFilter Field:=6, Criteria1:=ei
     .AutoFilter Field:=7, Criteria1:=eh
    

    becomes something like

    For iFilter = LBound(eFilters, 2) To UBound(eFilters, 2) '<--| loop through 'eFilters' array columns  
        .AutoFilter Field:= someColumnIndex, Criteria1:=someCriteria 
    Next
    

    where someColumnIndex and someCriteria are to be, correspondingly, connected to current inner loop iterator and stripped off eFilters current row (from outer loop) array

all what above could result in the following code:

Sub Testingloop()

    Dim eFilters As Variant, eVals As Variant
    With Sheets("looping table")
        eFilters = .Range("O3", .cells(.Rows.Count, "I").End(xlUp)).Value
        eVals = .Range("P3:Q" & .cells(.Rows.Count, "I").End(xlUp).Row).Value
    End With

    Dim iFilter As Long, ieVals As Long
    Application.ScreenUpdating = False
    With Sheets("looping").UsedRange
        For ieVals = LBound(eFilters, 1) To UBound(eFilters, 1)
            For iFilter = LBound(eFilters, 2) To UBound(eFilters, 2)
                .AutoFilter Field:=1 + iFilter - LBound(eFilters, 2), Criteria1:=Application.Index(eFilters, ieVals, 0)(iFilter)
            Next
            If Application.WorksheetFunction.Subtotal(103, .Resize(, 1)) > 1 Then
                With .Resize(.Rows.Count - 1, 1).Offset(1).SpecialCells(xlCellTypeVisible)
                    .Offset(, 7).Value = Application.Index(eVals, ieVals, 0)(1)
                    .Offset(, 8).Value = Application.Index(eVals, ieVals, 0)(2)
                End With
            End If
            .AutoFilter
        Next
    End With
    Application.ScreenUpdating = True

End Sub

For a start:

Sub Testingloop()
' Move this to the top. It doesn't affect your code, but it is good practice
' to put statements like these at the top and bottom of your code to make them
' easy to find.
Application.ScreenUpdating = False 

' This should be a number type and not a string
Dim endrown As Long 

Dim ex As String
Dim ez As String
Dim eh As String
Dim eg As String
Dim el As String
Dim ee As String
Dim es As String
Dim ef As String
Dim ei As String
Dim i As Integer
Dim LastRowColumnA As Long

' Better method of loading in multiple args, this will allow you to get
' all of your args in one go, and thus will speed up performance a bit.
' Practicing this early will also make it easier to develop more complex
' projects in the future.
Dim arrArgs as Variant 

' Create objects to hold the main workbook and worksheet you reference
' This allows for accurate range references.
Dim wb as Workbook, Dim ws as Worksheet

' Thisworkbook refers to the workbook containing the code.
Set wb = ThisWorkbook
Set ws = wb.Sheets("looping")

' Create a variable to hold the usedrange.
Dim rUsed as Range

' Qualified your cells reference with 'ws' to ensure the proper range is set
LastRowColumnA = ws.Cells(ws.Rows.Count, 1).End(xlUp).Row

ws.Activate ' Use Activate over select, but it is best to avoid either

endrown = ws.Range("I1000").End(xlUp).Row
    For i = 3 To endrown
        ' When referring to the same object repeatedly, use a with block
        ' This does a few things, first it allows your code to skip evaluation
        ' of your 'ActiveSheet' reference since it is already told where to look.
        ' It also makes your code easier to read, cleaner, and more efficient.
        With ws
            ee = .Cells(i, 9).Value ' Be sure to qualify your cells references
            ex = .Cells(i, 10).Value
            ez = .Cells(i, 11).Value
            es = .Cells(i, 12).Value
            ef = .Cells(i, 13).Value
            ei = .Cells(i, 14).Value
            eh = .Cells(i, 15).Value
            eg = .Cells(i, 16).Value ' I am assuming you intended to get the value here
            el = .Cells(i, 17).Value
        End With

        ' Instead of referring to the different ranges you could do something like
        ' arrArgs = ws.Cells(i, 9).Resize(8, 1).Value


        ' Using a declared variable is good practice, and may improve performance slightly
        Set rUsed = ws.UsedRange
        With rUsed
             .AutoFilter Field:=1, Criteria1:=ee
             .AutoFilter Field:=2, Criteria1:=ex
             .AutoFilter Field:=3, Criteria1:=ez
             .AutoFilter Field:=4, Criteria1:=es
             .AutoFilter Field:=5, Criteria1:=ef 
             .AutoFilter Field:=6, Criteria1:=ei
             .AutoFilter Field:=7, Criteria1:=eh
        End With

        On Error Resume Next
        With ws
            .Range("H2:H" & LastRowColumnA).SpecialCells(xlCellTypeVisible).Value = eg
            .Range("I2:I" & LastRowColumnA).SpecialCells(xlCellTypeVisible).Value = el
            .ShowAllData
        End With
    Next i
End Sub

This won't make a tremendous impact on performance, but it will make your code easier to work with. I also strongly encourage you to use the array instead of creating a separate string for each value you need to filter by. Again, not a big performance impact, but a good start on improving your coding.

Finally, depending on what your code is attempting to do you could try performing the operations in an array. You may also want to consider changing the calculation mode of the worksheet to xlCalculationManual (or something like that).