Leah is the name of Prophet Ya`qub's wife in the Hebrew Bible, I couldn't find any information on this name from Islamic sources, for this reason it cannot be used as a name for Muslims since it belongs to the Christians and Jews (Muslims don't use the name Benjamin even though the Bible says it is the name of Prophet Yusuf's brother, since it is not mentioned in Islamic sources). However, in Arabic Liyaa' means a land far from water, Liya is a type of bean or something similar that is very white, and when it is said about a woman "she is like liya" it means she has very white skin. Liya is also a valley in at-Ta'if, a city near Makkah in Saudi Arabia. Therefore you can use Liya as a name for girls if by it you mean these two things rather than the Biblical meaning.
Shazia means rare, precious, unique, and it is actually Shadhiyah, the "dh" is like in Dhikr. But you can also say Shazia as it is easier to pronounce this way.