Instead of gzip try bgzip. On Ubuntu install with

sudo apt-get install tabix

Example decompression of 161.7 GB file to 512.1 GB with 8 threads :

time bgzip -d --threads 8 win1_nvme01n1.img.gz 
 
real    70m56,540s
user    15m50,506s
sys     4m26,017s

• Ubuntu 22.04.2
• bgzip 1.13+ds

• https://www.youtube.com/watch?v=K75Kc5EyB8Y