Israeli officials estimate there are 1,300 tunnels, spanning 300 miles across the Gaza Strip, which itself is just 25 miles long. The military describes the network as one of the most elaborate underground webs in the world. It says there are underground bunkers beneath Gaza hospitals. Palestinian doctors have denied this.
https://www.washingtonpost.com/world/2023/11/03/gaza-tunnels-hamas-israel-war/
What we know about Hamas’ 300-mile tunnel system below Gaza
https://nypost.com/2023/11/08/news/what-we-know-about-hamas-300-mile-tunnel-system-below-gaza/
Estimates vary widely, but as of October 2021, Hezbollah's leader Hassan Nasrallah claimed his organization has 100,000 trained fighters; while in 2017, Jane's assessed Hezbollah's strength at more than 25,000 full-time fighters and approximately 20,000–30,000 reservists.