N1
を兼ねて
をかねて
And also, Also (partly) to, Also (partly) for (the purpose of), At the same time, To double as, When … also, While … as well, And as
日本語の勉強を兼ねて、英語の字幕なしで日本の映画をみています。
I watch Japanese films without English subtitles, partly as Japanese practice.
Explanation
「を兼ねて」 means 'doing one thing while also serving another purpose', killing two birds with one stone.
Examples: 「散歩を兼ねて買い物に行く」 (I go shopping, which also serves as my walk), 「親孝行を兼ねて旅行する」 (I travel, also as a way to be good to my parents).
The noun before it is the extra purpose, and the verb after it is what you actually do. It often appears as 「も兼ねて」; before a noun, use 「を兼ねた+noun」.
Mixed up with
「を兼ねて」: both purposes matter and are planned on purpose, a true 'two in one'.
「がてら」: follows the stem of a movement verb or a noun (散歩がてら); the main action is what counts, and the other is a quick extra.
「ついでに」: casual 'while I'm at it'; it lacks the formal double-purpose feeling of 「を兼ねて」.