Tā tí chū le liǎng gè lǐyóu, qí èr gèngjiā zhòngyào.
He raised two reasons, and the second one is more important.
Tips
grammar
其二 is used in formal or written enumeration. It pairs with 其一 (firstly), and can continue with 其三 (thirdly), 其四 (fourthly), etc. Equivalent to 第二 (second) but more literary in tone.