XL 2019 Somme de cellules.

Option Explicit
Function MaxGroupes(ByVal Rng As Range) As Double
   Dim Cel As Range, S As Double
   For Each Cel In Rng
      If Cel.Value <> 0 Then
         S = S + Cel.Value
      Else
         If MaxGroupes < S Then MaxGroupes = S
         S = 0
         End If
      Next Cel
   If MaxGroupes < S Then MaxGroupes = S
   End Function

Option Explicit
Function MaxGroupes(ByVal Rng As Range) As Double
   Dim Cel As Range, S As Double
   For Each Cel In Rng
      On Error Resume Next
      If Cel.Value <> 0 Then
         S = S + Cel.Value
      Else
         If MaxGroupes < S Then MaxGroupes = S
         S = 0
         End If
      Next Cel
   If MaxGroupes < S Then MaxGroupes = S
   End Function

Function BiSomme(rng)
    Dim rev As Boolean, v1&, v2&, I&
    For I = 1 To rng.Cells.Count
        If rng.Cells(I) = 0 Then rev = True
        If rev = False Then v1 = v1 + rng.Cells(I) Else v2 = v2 + rng.Cells(I)
    Next
    BiSomme = Array(v1, v2)(Abs(v2 > 0))
End Function

Private Sub Worksheet_Change(ByVal Target As Range)
Dim dercol%, c As Range, deb As Range, s#, plage As Range, plagemax As Range, smax#
dercol = Cells(1, Columns.Count).End(xlToLeft).Column
Rows(1).Interior.ColorIndex = xlNone 'RAZ
For Each c In Cells(1).Resize(, dercol)
    If Not IsNumeric(CStr(c)) Then Application.EnableEvents = False: c = 0: Application.EnableEvents = True
    If deb Is Nothing Then If c <> 0 Then Set deb = c: s = 0
    If Not deb Is Nothing Then
        If c <> 0 Then
            Set plage = Range(deb, c)
            s = s + c
        Else
            If s > smax Then Set plagemax = plage: smax = s
            Set deb = Nothing
            s = 0
        End If
    End If
Next
If Not deb Is Nothing Then If s > smax Then Set plagemax = plage: smax = s
If Not plagemax Is Nothing Then plagemax.Interior.ColorIndex = 6 'jaune
ThisWorkbook.Names.Add "somme", smax 'nom défini
MsgBox "Somme maximum entre zéros " & [TEXT(somme,"[h]:mm")]
End Sub