It’s no more separate than a parasite or a tumor. It’s entirely dependent upon the host for life. Everything it does from conception on is entirely dependent upon the host/mother.
Someone in a vegetative state is no less human than you are, but their quality of life and awareness may differ and so we can judge if that quality should be maintained or terminated.
If they were no less “human” than I am, there would be no one who could dictate over whether they live or die. The very fact that their “humanity” is in question is why you are wrong.
So too with the lowly zygote - human, alive, with or without a CNS, but developmentally incapable of controlling it’s existence or continuence. That’s left up to the will of the host.
Women miscarry all the time, every day, through no “will” of their own. It can be a woman’s most ardent wish to have a baby, but no, they have a “hostile environment” down there & there’s often nothing they can do about it.
If a zygote created through intercourse is just as “human” as you or I, what about a zygote created in a lab? A women goes in for some artificial insemination, a in vitro lab tech takes a batch of sperm and 20 eggs and fertilizes them but the doctor only calls for 10 and tells him to dispose of the rest. Is the lab tech now guilty of manslaughter?
A sperm has the potential to create life. Am I guilty of murder every time I masturbate or have a nocturnal emission? Is my girlfriend guilty of cannibalisms when she grants me oral pleasure?
Lets be reasonable, it takes an actual fetus to get close to “humanity”, a zygote is not even close.