I use SSD and HDD. System is installed on SSD and HDD I use as home for files. Both disks are formated as EXT4. Do you as Zorin users defrag your disks?

Which software do you use?

There really is no need to defrag on Linux. There are apps available that claim to do so, but they are not useful unless you wish to organize Blocks of data for some immediate purpose.
Windows writes to the drive based on First Available Space. Linux looks at the size of a file, then allocates the right space for it, with room to grow. If the file outgrows its space (which would cause it to become fragmented, the entire file is then Moved to a New Allocated space with a larger size and room to grow.