I think for the Italians it was simply one more disaster in a disasterously unsuccessful war bid made by Mussolini. From the German point of view it should have been seen as irrelevant.
Yugoslavia was neutral Romania was already allied with Germany and likely Germany could have kept Bulgaria neutral rather than trying to ally with them. This means that even if Britain comes to Greece's aid and defeats the Italians in Albania what does this buy them? It is Gallipoli on a giant scale. The British cannot support a large air force in Greece, let alone a large ground force.
A better alternative is to simply allow the campaign to run its course for the Germans. Maybe give up an infantry division or two to prop up the Italians.
Then, carry out Barbarosa as planned rather than go through a diversion campaign into the Balkians. Without a partisian campaign going on in Yugoslavia and with no substancial garrison required for this region the Germans are far better off in their Russian campaign, not to mention gaining valuable summer and fall fighting time.