not to mention
Without ever needing to speak of; in addition to; besides. — Used to add something to what you have said or explained.
Dave is handsome and smart not to mention being a good athlete.
They have three fine sons, not to speak of their two lovely daughters.
Sally takes singing and dancing lessons to say nothing of swimming and tennis lessons.
Compare: LET ALONE, TO SPEAK OF.
Source: A Dictionary of American Idioms