How do you ssh using zstd dynamic compression?

I want to set up my ssh tunnel to do dynamic compression so that I get maximum throughput for the bandwidth and CPU resources I have available on each end. Since gzip compression is built-in and not pluggable I thought I could use -o ProxyCommand to set up a double ssh tunnel where the outer tunnel sends compressed data as the content and the inner tunnel connects to the ssh daemon on the remote host. This *almost* works. Here is my command:

# dynamic compression parameters to zstd omitted for brevity
ssh -o ProxyCommand='zstd | ssh -p %p %h "unzstd | nc localhost %p | zstd" | unzstd'

Here are some things I know about this command: - When I run this command the terminal hangs without any output. - It works if I remove [un]zstd, which is not surprising since using netcat as the proxy command is a standard method to connect through jumphosts - cat | zstd | cat at a command prompt will not return data immediately because compression programs process data in chunks. You have to send EOF with ctrl+d a couple times before it releases the compressed data. You can decompress the data within the pipeline as well and it works the same. - If I hit ctrl+d when running the full command nothing happens. What am I missing here? Is there a way to make this work or another way I am overlooking?