For one thing… for another… (一则…二则)

Structure 一则 + reason 1，二则 + reason 2 （…三则…）

一则…二则… (yīzé… èrzé…) lists two (or more) reasons for the same fact: "for one thing…, for another…". 他没去，一则没空，二则不感兴趣 = "he didn't go: for one thing he had no time, for another he wasn't interested". It is the more cultivated, written cousin of 一来…二来… (HSK 5), which sounds more colloquial; the meaning is identical, but 一则…二则… belongs to essays and the press. It can extend with 三则…. 则 is read zé.

Examples

他tā没méi去qù，一yī则zé没méi空kòng，二èr则zé不bù感gǎn兴xìng趣qù。
He didn't go: for one thing he had no time, for another he wasn't interested.
搬bān到dào郊jiāo区qū，一yī则zé房fáng租zū便pián宜yi，二èr则zé空kōng气qì好hǎo。
He moved to the suburbs: for one thing the rent is cheap, for another the air is good.
公gōng司sī决jué定dìng缓huǎn发fā新xīn品pǐn，一yī则zé资zī金jīn不bù足zú，二èr则zé时shí机jī未wèi到dào。
The company decided to delay the launch: for one thing funds are short, for another the timing isn't right.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.