So in the setup as shown, where would you add fuse or circuit breaker protection? Would it be on the 1/0 between the Blue Sea Switch and the + Distribution block, 150 amp? Also on the 6ga connection from the Blue Sea Switch to the Main House Buss, using the 50 amp circuit breaker installed currently?

I am redrawing the diagram with the HU and ZLD connected to a positive and ground strip. I'm adding a fuse between the distribution block and the positive strip. Any thoughts on fuse size for the HU and the ZLD?