Hello Niwantha,
Yes, it is perfectly acceptable to use "contained" in the sentence you provided. The sentence conveys that all the resumes received up to the present moment are located or included within the attached zip folder. "Contained" is used as a past participle in this context, indicating that the resumes are enclosed or enclosed within the folder. Overall, your sentence is grammatically correct and effectively communicates the intended meaning.
I hope this helps! If you have any more questions, feel free to ask.