Export a bit of the video, encode that bit with zarxgui, delete the first lossless, export the second bit, encode that second bit, delete lossless, etc, until you have the whole timeline exported and converted. Then import the first encoded bit in mkvmerge gui, then click appena, select the second bit, click append, select third, etc, then select how to name and where to save the mkv and click start muxing.
