That's BS; because the older a child gets, the stronger and more viable it is.
Using the idea that a zygot isn't viable and is therefore not alive, is a strawman; because we could then take newborns and leave them alone, exposed to the elements for 1 or 2 days, and those that live we can then say they were viable.
I just pointed out to you that we do not do that to those on life support. We do not consider viability to that degree necessary for anybody who is ill. Since the point is that the zygote should be more viable than the brain dead, no one is calling for that amount of viability.
Your point is worthless. I don't argue we should toss grandma into the middle of the woods just because she slips in the bathtub either.