を兼(か)ねて

を兼(か)ねて is a grammar pattern that makes use of the standard meaning of the る-Verb 兼(か)ねる 'to stretch across to', or 'to do concurrently'. The adverbial particle を will mark a noun which will be considered the secondary event or state, while 兼(か)ねて will be followed by the primary event or state that will be done concurrently with (A). This is often translated as 'to (A) at the same time as (B)', 'to double as (A)', or 'to (A) also partly for the purpose of (B)'.

• おばあちゃんはボケ防止(ぼうし)を兼(か)ねて、毎日(まいにち)クロスワードパズルをしています。
  My grandma does crossword puzzles also partly to prevent dementia.
• 日本語(にほんご)の勉強(べんきょう)を兼(か)ねて、英語(えいご)の字幕(じまく)なしで日本(にほん)の映画(えいが)をみています。
  I watch Japanese movies without subtitles also partly to learn Japanese.
• ダイエットを兼(か)ねて、毎朝(まいあさ)ランニングしています。
  I run everyday also partly to lose weight.

を兼(か)ねて often highlights (B) as the primary goal, where (A) is something that acts to support it, makes sense to be done together, or just gives the speaker a good excuse to do (B). In order to remember that (A) is actually the secondary goal in this structure, using the literal translation of 'while extending across to (A), (B)' may help.
In the case of multiple goals existing, the case-marking particle と will be used for listing of nouns.

• 運動(うんどう)不足(ぶそく)とストレス発散(はっさん)を兼(か)ねて、キックボクシングジムに通(かよ)っている。
  I go to a kickboxing gym also partly to relieve stress and to get exercise.
• 体調(たいちょう)管理(かんり)と節約(せつやく)を兼(か)ねて、寝(ね)る時(とき)はエアコンを使(つか)わないようにしている。
  I try not to use the air conditioner also partly for my health and to save money.