Public Function zzz10() As String
    s = "111111 5555%5555 6666 7777%3456789 65678 5678%789878"
    s = " " & s & " "
    With CreateObject("VBScript.RegExp")
        .Global = True
        .Pattern = "\s{0,1}\d{0,9}[%]\d{0,9}\s{0,1}"
        zzz10 = Trim(.Replace(s, " "))
    End With
End Function

Public Function zzz11() As String
    s = "111111 5555%5555 6666 7777%3456789 65678 5678%789878"
    s = " " & s & " "
    With CreateObject("VBScript.RegExp")
        .Global = True
        .Pattern = "\s\d{0,9}\s"
        zzz11 = Trim(.Replace(s, " "))
    End With
End Function

?zzz10
111111 6666 65678
?zzz11
5555%5555 7777%3456789 5678%789878