Lemon Zest is really one of the best mangoes available, IMO. I've had mine now about 5 maybe 6 years and the fruit are just delicious every year. You will have to spray fungicide to get good crops, I got about 70 from a 15 ft tree, just sprayed lower part that I could reach and only once with sulfur. Upper canopy did not have many mangoes, probably from PM infection of flowers. But it is definitely possible to get a decent crop. In relation to your other question, it should not put your other trees more at risk. Powdery Mildew proliferation depends on weather, all trees will be at risk. Some trees are just better at setting fruit through the infection. LZ is just more susceptible to it. I would get it.