Even something as simple as the sound of the letter a, has many different pronunciations, so it's difficult.
この場合、次のように言うと良いと思います。
ーEven something as simple as the sound of the letter a, has many different pronunciations, so it's difficult.
「文字aの音1つをとっても、多くの発音があって難しいです」
even something as simple as ... で「…の一つをとっても」を表現できます。
pronunciation で「発音」
ご参考まで!