Newton Firezone command is used by Newton turrets in order to get them to target a specific area. Notice, that setting a firezone wont stop a turret with fire-at-will setting from firing at enemies entering its range (however it will realign to aim at firezone while idle). As a confirmation of firezone setup turrets will fire at the center of choisen area (beware, that a turret failing to do so might mean that firezone is obscured or unreachable). Any targets entering a firezone, including friendlies, will be targeted.
This command is useful in a couple of scenarios, for example you can set up your turrets to target only specific area of terrain (such as cliffs or edges of islands).
Remember, that depending on units mass you might require more Newton turrets. Not all units will be eligible to be "delivered" that way, as most will die from fall damage. The usual choice are Jumpbot Factory units, as most of units from this factory negate fall damage (and Jack specifically). Lead units in one-by-one, as otherwise they may be launched either by not every turret at once (providing insufficient force), or from a wrong location (and into wrong direction respectively)