Never heard of the CANT Z 511, seems like a promising aircraft as it could take off and land fully loaded in rough seas.
nhungdoicanh: CANT Z.511
Never underestimate your allies.
The summary of specifications is that its best cruise was 300 km/h and that it had a flyout of 13 hours one way, an effective patrol radius of 4.5 hours and a time on station of 3 hours with 30 minutes RTB reserve. Best altitude was about 3000-5000 meters. Crew was 6 men. Had it been militarized, as Benny the Moose desired, it would have delivered frogmen teams on powered torpedoes to attack port shipping.
More practically, it was a candidate for an Axis equivalent to a Sunderland flying boat. It was designed to set down and be refueled open ocean.
And then there is this candidate...
The Piaggio P108 was the only heavy four-engine bomber to see service with the Regia Aeronautica during World War Two. It was an innovative design.comandosupremo.com
Summary on this aircraft... similar specifications to the CANT Z.511 overall with a 6 or 7 man crew, capable of 4.5 hours flyout, 2 hours on station and 2x the warload. She worked. I think the bomb bay was designed to carry 45 cm (17.7") Si 200/450 x 5.36 Silurificio torpedoes. (Coffin nails).
Maritime strike bird all ready to go in 1941.
I've previously suggested that the German ditch their shitty He 177 and just build P.108s under license as their heavy bomber. AFAIK the Germans in OTL operate a couple P.108s as transport aircraft late in the war, after Italy fell to the Allies.
There was also a version of the P.108 with a 102mm anti-ship cannon, I think this one might be the marine patrol plane you're looking for.