not only ... but also ...; ... is true, but even more ...
Used in the pattern AもさることながらB to acknowledge A while emphasizing B. Often translated as 'not only A but also B' or 'A is certainly true, but B is even more so'. The phrase is a fixed expression and cannot be broken down productively.
He is talented, to be sure, but his effort is also extraordinary.
This restaurant has great food, but the service is also wonderful.
もとより means 'from the beginning' or 'of course', and is used to state something obvious before adding another point. もさることながら explicitly acknowledges the first point while emphasizing the second.
はもちろん means 'not to mention' or 'let alone', and simply adds another item without the nuance of emphasizing the second point over the first.
Kanji spelling using 然る; less common but still encountered.
Variant with 事; rare.
Variant with 乍ら; very rare and archaic-looking.
Derived from the classical Japanese adjective 然り (さり, 'to be so') in its attributive form 然る (さる) combined with the particle も and the concessive ながら. The phrase literally means 'while it is so, ...' and developed into a fixed pattern for acknowledging one point while emphasizing another.