The top seeds lost their opening match on Sunday but hit back to beat German pair Kevin Krawietz and Tim Puetz 7-6(9) 6-2 in Turin's Inalpi Arena to stay on course for the semi-finals.
Whatever happens for the rest of the week, it has been a sensational first full year together for the former US college players who have claimed seven Tour-level titles, including winning Wimbledon and the Masters 1000 in Canada.
"It's been one crazy year, that's for sure," Cash said after lifting the Year-End ATP Doubles No. 1 trophy on court.
"We put an awful lot of work in during the off-season. We've ticked off so many things this year and I think we both truly believed at the start of the year that this was possible for us and to be standing here now is very surreal."
Their Wimbledon title made them the first all-British men's pair to win a Grand Slam title since 1936.
They will now hope to crown the year by winning the title in Turin, but will need to beat Marcel Granollers and Horacio Zeballos on Thursday to qualify from the group.