Slow run when large pyz file

I have "shived" all my dependencies (pandas, scipy, ...) to end up with a compressed .pyz file of close to 200MB.
My entry point is a function that does not import anything but modules from the sdlib (sys, pathlib) and runs immediately when run outside the shiv file.
However, when I run the shiv file, it takes 16s to run (once it has already been decompressed in the .shiv folder, for the first run, it takes 82s to decompress to ~600 MB and run)
Is there some way to improve this performance ?
Is the .pyz file completely read from disk & uncompressed each time the pyz file is run (even if it is only to check it has already been decompressed in the .shiv folder) ?
If so, would it make sense to split the file in two file, a small .pyz with the bootstrap logic (check .shiv/... folder is updated, run preamble,...) and a large file with the zipped site-packages that would only be accessed if there is a need to decompress for the first time to the .shiv folder ?

The issue names no repository files or tests; start by tracing the shiv bootstrap path, including the .pyz read, the .shiv directory check, and first-run decompression. Compare subsequent execution with initial extraction, and define done as avoiding unnecessary work on later runs without breaking dependency extraction.