Compared to the other years' winter vacations, this year's has become shorter. And work has already started from today.
ご質問ありがとうございます。
"Compared to the other years' winter vacations,"＝「例年の冬休みと比べると」
"this year's has become shorter."＝「今年のは短くなった。」
☆"this year's"とは"this year's winter vacation"の省略です。
"And work has already started from today."＝「そして今日から仕事が既に始まっている。」
ご参考になると幸いです。
I didn't have as many days off over the holidays this year, and I had to go back to work today.
ーI didn't have as many days off over the holidays this year, and I had to go back to work today.
「今年は休みが例年より少なかって、今日仕事に戻らなければいけなかった。」
I didn't have as many days off over the holidays this year は直訳すると「今年は休暇中に同じ数だけの休みがなかった」＝「休みが例年に比べて少なかった」と言えます。
go back to work で「仕事に戻る・仕事を再開する」
ーMy holidays were shorter than usual this year, and I'm already back at work.
「今年はいつもより休暇が短くて、もう仕事に戻っている。」
my holidays were shorter than usual で「休暇がいつもより短かった」
already back at work で「すでに仕事に戻る」
ご参考まで！
アメリカ合衆国 
カナダ 
