To be honest, silver gaze is not a technique that is centered on seeing liquid.
This was making it hard for Zain to see his blood and what it entails.
Unlike one's core which is made of aura, inherited magic isn't in form of aura but rather, it lies in the blood.
If the blood was a solid, he would have veiled his vision an force his eyes to adapt to seeing more on solid but unfortunately, he couldn't because blood is liquid.
Techniques are extremely broad and nearly impossible for one to comprehend all the different portion of it, except the person is smart, gifted or talented like Harry and not like Zain. Zain is just the inverse.
If maybe he was as gifted as Harry, he would have been able to find a way to refine the silver gaze technique.
