What Zha is
Zha (ژ) is not one of the twenty-eight letters of the Arabic alphabet. It is one of four letters Persian added to the Arabic script in order to write sounds Arabic does not have, and it spread with the script into Persian, Urdu, Kurdish and Central Asian Turkic.
Arabic has no zh. It maps to ز, and Persian formed ژ by giving ز three dots.
How Ilm ul Huroof reads Zha
It does not read it directly, and this is worth stating plainly. The Science of Letters was built on the twenty-eight Arabic letters, each tied to an element, a divine name and a numerical value in the abjad. The four Persian letters postdate that framework and have no classical reading of their own.
What the tradition does is read the Arabic base letter beneath the added dots. For Zha, that base is Zayn (ز), and a name written with Zha is read through Zayn's qualities and abjad value.
Anyone offering you a separate classical reading for Zha is inventing it. We would rather tell you where the tradition stops.
Zha in names
Names carrying Zha are usually Persian, Turkic, Urdu or Pashto in origin rather than Arabic. On their AsrNaam pages the letter grid shows Zha as written and reads it through Zayn.
Browse all letters, read the introduction to Ilm ul Huroof, or see why a name's Urdu spelling matters.
Zha is a Persian letter, one of the four Persian added to the Arabic alphabet, and like the ra it is built on it joins only to the right. It accepts a connection from the letter before it but never passes one on, so it has no initial or medial shape, and the letter after it always starts fresh.
Zha is a moon letter. When the definite article ال (al-) comes before it, the l is pronounced clearly and stays audible, as in القمر, al-qamar, the moon, which gives this group its name. Names beginning with Zha keep their al- intact when they carry one.