Simply Enter the following the Ubuntu Terminal
sudo su
sudo apt update
sudo apt-get install cmake make gcc g++ flex bison libpcap-dev libssl-dev python3 python3-dev swig zlib1g-dev
sudo apt install python3-git python3-semantic-version
sudo apt install curl
sudo apt update
echo 'deb http://download.opensuse.org/repositories/security:/zeek/xUbuntu_20.04/ /' | sudo tee /etc/apt/sources.list.d/security:zeek.list
curl -fsSL https://download.opensuse.org/repositories/security:zeek/xUbuntu_20.04/Release.key | gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/security_zeek.gpg > /dev/null
sudo apt update
sudo apt install zeek-lts
Now Return to the ReadMe.MD