Chick is not the same as a chicken. An embryo is not the same as a chick, a fertilized egg is not the same as an embryo. And finally, a fertilized egg is not the same as a chicken.
Their genome is the same but they are not the same.
Of course organisms are not "the same" at each stage of their life cycle. That is not the point and your language remains sloppy. You are not the same as you were 10 years ago or the same as you will be 10 years hence. Nevertheless you are human aka homo sapien at all points in your changing life and entitled to basic human rights throughout.
Similarly the chicken is not the same at the various stages of its life but it is still a chicken Gallus gallus domesticus throughout each stage of its development and life.
Your problem is you want to take a portion of the homo sapiens species and arbitrary declare it non human based presumably on your personal desire to profit directly or indirectly via the scientific gains you feel the death and dismemberment of such individuals will afford you. That is wrong but you have somehow blinded yourself to that fact.
Ok, at least you understand that they are not the same.
So a fertilized human egg is not THE SAME as a human being, right? Do you agree?
No two people are exactly the same. So, which of them are human and which aren't?
The DNA of the fertilized egg is the same as the DNA of the adult. Both are human. They are simply at different stages of their life.
Two people are human beings. Two fertilized human eggs are two fertilized human eggs.
A fertilized human egg is not THE SAME as a human being (a newborn child), right?
Fertilized human eggs are not the SAME as human newborn babies from which they have developed, right?