No you can't make up definitions. A zygote is not a child. By definition.
Yes, let's talk about definitions. A human zygote is human, just like an elephant zygote is elephant.
An abortion is not murder.
Abortion is the word used for early termination of a pregnancy. Not all abortion is murder, because the word is also used for miscarriages (spontaneous abortions), but intentionally terminating a pregnancy is killing a human being. If the killing accords with the definition of murder, then it is murder, right? That's what definitions are all about.
"Child" isn't required for it to be murder. "Human being" is. Calling it a "zygote" or "embryo" or "fetus" or even "blob of tissue" doesn't stop it from being a human being. All of those words (except "blob of tissue") describe a stage of development, and when we are talking about stages of development of humans, all of those still mean "human being". Intentional killing of a human being with malice is murder.
Definition:
Murder--To kill a human being with premeditated malice.
"Kill" requires that the victim be alive, and that is without question.
"Human being" is also without question. It has human DNA, it is from humans and will be recognizable as a human early on in the pregnancy. A misshapen or malformed or maimed human is still a human being.
"Premeditated" requires merely planning, and walking into an abortion clinic is part of that planning.
"Malice" is ill will toward the victim without reason or cause.
MAL'ICE,
noun [Latin malitia, from malus, evil.] Extreme enmity of heart, or malevolence; a disposition to injure others without cause, from mere personal gratification or from a spirit of revenge; unprovoked malignity or spite.
By definition. Change the definitions to suit your argument and your argument immediately becomes worthless.
So, are you willing to stick by that statement? Since you attempted to change definitions of terms to suit your argument, are you willing to admit that your argument is worthless?