+1 to all the guys saying flush cuts for zip ties. the idea you need "high leverage" to cut plastic is simply not true.
from there, figure out what you need for the steel. I really like knipex hard cutting jaws, they make a wide variety. you can get anything from bolt cutters (compact bolt cutters, ie co-bolts). The higher leverage cutters have narrower opening, so you need to size the jaws correctly.
The co-bolts now have a 160 size and the high leverage diagonals also come in 160. But you also need to think about the number of repetitions, the size or your hands, and basic ergonomics. 160 is good for packing into portable kits, for shop use a 180 is typically more comfortable.
Also, if you are doing lots of cuts (eg zip ties) spring loaded is way better.
KNIPEX Diagonal Flush Cutters provide a fully flush cut in plastic, soft metals and molded plastic components from spruces.
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Removing your drum brake shoe is made easy by selecting this affordable KNIPEX CoBolt Compact Bolt Cutters.
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For shop use, these are arguably more comfortable...but slightly larger size (7" vs 6").
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