1. Even if Mussolini does bluff, I am not sure if such an aggressive step wouldn't be premature. How wary of Germany would France be? Would it be a quickstart into war-readiness? Also, an invasion of Austria (which would meet resistance, opposite to 1938) would give a wholly different image to the NS-aim of uniting the "Volksdeutsche" within the Reich. The CSR would certainly receive more backing and there would be no Munich. Also, Mussolini would be severely annoyed and might not be willing to enter an alliance with Berlin later on.
2. If Mussolini does not bluff, he will probably overwhelm the German army. In 1934, Italy would
- possess more airplanes (there would not yet be an official German Luftwafffe)
- the same applies to tanks
- Italy would have more manpower, Germany would yet not have officially re-introduced the draft and would have to rely on the 100,000-men Reichswehr, WW-1-veterans and militia cadres (i.e. the SA)
- have the possibility to diplomatically isolate Germany
I reckon that while the Austrians would delay a German advance towards Vienna, the Italians would, with Austrian backing, simply move northwards from the Brenner. Tyrolia's capital Innsbruck could be reachable within hours for an Italian vanguard - and being there means half the way to the German border already.
Splitting there, Italy could test several routes into Germany: Fernpass, going via Scharnitz to Garmisch or simply go the long way down the river Inn. Wherever a breakthrough can be achieved, this would not only mean entering the Reich, but also to leave the more mountaineous parts of the Alps.
From there, it is less than 100 km to Munich. Now logistics count: how many troops can be supplied through the Alps? Also, can the Italian airforce manage air-superiority from their bases in Northern Italy? If so, Munich will be the first city in Europe to prove Douhet, day by day.
If the Italians manage to reach Munich (they should under the given circumstances- but on the other hand, they are Italians; it would be historical irony of the highest degree if they acted competenly if having a war against Hitler's regime), then it is game over for the Anschluss...
Going from there