# 1-) Looking for txt files older than 365 days and printing them within folder and subfolder
 find . -name "*.txt" -mtime +365

# 2-) Printing txt files modified less than 365 days ago within folder and subfolders
 find . -name "*.txt" -mtime -365

# 3-) Printing txt files modified 365 days ago within folder and subfolders
 find . -name "*.txt" -mtime 365

# 4-) Removing txt files older than 365 days within folder and subfolders
*(if you want to remove files is advisable to be sure about files listed/found by "find...")
 find . -name "*.txt" -mtime +365 -exec /bin/rm -f '{}' +

About -mtime: (-mtime n)
(+) means greater than, (-) means less than, and without any symbol means exactly equal to.

#1-) Looking all txt files within folders and its subfolders and compress them in a unique zipped file (Compressed_Files.zip)
 find . -name "*.txt" -print | zip Compressed_Files -@

# 2--)Compressing each txt file within folder and subfolders file, adds to original name ".gz" (filename.txt to filename.txt.gz) 
# and deletes original file
 find . -name "*.txt" -exec gzip -f '{}' +

# 3-)Unzipping each txt files within folder and its subfolders, deleting original gz file.
 find . -name "*.txt.gz" -exec gunzip -f '{}' +

 # 1-) Removing zero size files within folder and its subfolders.
1-) find . -type f -size 0 -exec /bin/rm -f '{}' +
or
2-) find . -type f -empty -exec /bin/rm -f '{}' +