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