Shlomo Zalman HaLevi (Steinberger) - גר"א כּנכד

Correction,:
אם שׁכּן, אז היאך!!?!

I’m not sure what Ga’a is? You will need to explain more what you want to know. If you can write in English it would be easier for me.

The Vilnius/Vilna Gaon/Genius, Rabbi Eliyahu, "Gaon of Vilna" הגר''א;
If he was a descendant of the Holly TaZ/TuZ.

Correction:
אֶפְשָׁר שֶׁ"הַגָרֶ"אֶ" היה נכד שלו?
אם כן, אז היאך?
יישר כחכם.

Oh, so sorry but that I do not know at this time.