PDAL
Install?? I used conda. You do not want to use conda.
pdal info points.laz
Compress:
pdal translate points.{las,laz}
Merge, while preserving 1 mm precision:
pdal merge all/*.laz all.laz --writers.las.scale_x=0.001 --writers.las.scale_y=0.001 --writers.las.scale_z=0.001
Custom fields
PDAL happily ignores custom fields. So does CloudCompare. Use laspy