I simplified everything. I even tried to do the tick conversion using only Zorro but the implementation was slow so I'll stick with the combination of Python and Zorro. I've also tried two new approaches which do not use the 'tac' command. They are slower but if you want to run the script on Windows without using Cygwin, it might help.

The Bash script and Python script are now merged into one: convert.py (it made sense to make it like this from the beginning but I wasn't that proficient in Python)

The two Zorro scripts for T1 and T6 data were also merged: ConvertData.c

The usage is similar, you can find more info here - you can skip directly to the "Usage" section.

After the initial setup it's possible to convert all .csv data for various assets to T1 and T6 formats (containing spread) using just one command. But please note the assets have to be present in AssetsFix file.