if statments with "AND , OR" - excel

Question

please i need help on this code: it compares different values in different column at the same row level and executes the "then statement". But the code i wrote doesn't real function as i expected.
Sub Z_status()
Dim wsO As Worksheet
Set wsO = Sheets("Sending List")
Dim i As Long
Dim Lastrow As Long
With wsO
Lastrow = Cells(Rows.Count, 5).End(xlUp).Row
'Lastrow_2 = Cells(Rows.Count, 6).End(xlUp).Row
'Lastrow_3 = Cells(Rows.Count, 3).End(xlUp).Row
'Lastrow_4 = Cells(Rows.Count, 8).End(xlUp).Row
For i = Lastrow To 2 Step -1
'For j = Lastrow_2 To 2 Step -1
'For k = Lastrow_3 To 2 Step -1
'For l = Lastrow_3 To 2 Step -1
Cells(1, 7).Value = "Expected state"
If (Cells(i, 5).Value = "MTS" Or Cells(i, 5).Value = "MTO") And (Cells(i, 6).Value = "1/1/1900" Or Cells(i, 6).Value > Date) And (Cells(i, 3).Value = 0) And (Cells(i, 8).Value = 0) Then
Cells(i, 7).Value = "Z1"
ElseIf (Cells(i, 5).Value = "MTS" Or Cells(i, 5).Value = "MTO") And (Cells(i, 6).Value = "1/1/1900" Or Cells(i, 6).Value > Date) And (Cells(i, 3).Value = 0) And (Cells(i, 8).Value > 0 Or Cells(i, 8).Value = 0) Then
Cells(i, 7).Value = "Z3"
ElseIf (Cells(i, 5).Value = "MTS" Or Cells(i, 5).Value = "MTO") And (Cells(i, 6).Value = "1/1/1900" Or Cells(i, 6).Value > Date) And (Cells(i, 3).Value > 0) And (Cells(i, 8).Value > 0 Or Cells(i, 8).Value = 0) Then
Cells(i, 7).Value = "Z5"
ElseIf (Cells(i, 5).Value = "Obsolete") And (Cells(i, 6).Value < Date) And (Cells(i, 3).Value > 0) And (Cells(i, 8).Value > 0 Or Cells(i, 8).Value = 0) Then
Cells(i, 7).Value = "Z7"
ElseIf (Cells(i, 5).Value = "Obsolete") And (Cells(i, 6).Value < Date) And (Cells(i, 3).Value = 0) And (Cells(i, 8).Value = 0) Then
Cells(i, 7).Value = "Z9"
End If
Next i
' Next j
' Next k
' Next l
End With
End Sub

Answer 1

1 Your conditions for Z3 and z5 are identical
2 You can write
(Cells(i, 8).Value > 0 Or Cells(i, 8).Value = 0)
as (Cells(i, 8).Value >= 0 )
Your ifs can be written more clearly as
If (Cells(i, 5).Value = "MTS" Or Cells(i, 5).Value = "MTO") And (Cells(i, 6).Value = "1/1/1900" Or Cells(i, 6).Value > Date) Then
If (Cells(i, 8).Value = 0) Then
Cells(i, 7).Value = "Z1"
Else
If (Cells(i, 8).Value > 0) Then
Cells(i, 7).Value = "Z5"
End If
End If
Else
If (Cells(i, 5).Value = "Obsolete") Then
If (Cells(i, 6).Value < Date) And (Cells(i, 8).Value >= 0) Then
If (Cells(i, 3).Value > 0) Then
Cells(i, 7).Value = "Z7"
Else
If (Cells(i, 3).Value = 0) Then
Cells(i, 7).Value = "Z9"
Else
'This case is undefined
End If
End If
Else
'This case is undefined
End If
Else
'this case is undefined
End If
End If
Hopefully you can work out the errors more easily in this form