Here, give the complete guideline for the compilation for the Zestcoin in Ubuntu 18.04 LTS

Dependency Build Instructions:

Build requirements:
sudo apt-get install build-essential libtool autotools-dev autoconf pkg-config libssl-dev

Install libboost-all-dev:
sudo apt-get install libboost-all-dev

Install Berkeley v4.8 Database Utilities:
sudo add-apt-repository ppa:bitcoin/bitcoin
sudo apt-get update

Install libdb4.8: (don’t install another version will break binary wallet compatibility and is not recommended.)
sudo apt-get install libdb4.8-dev libdb4.8++-dev
sudo apt-get install libminiupnpc-dev

Dependencies for the GUI:

For Qt 5 you need the following:
sudo apt-get install libqt5gui5 libqt5core5a libqt5dbus5 qttools5-dev qttools5-dev-tools libprotobuf-dev protobuf-compiler

Install libqrencode (optional):
sudo apt-get install libqrencode-dev

Now, After install Dependencies Build & GUI, go the directory where Zestcoin Downloaded and Unzipped:
For download Zestcoin, you can get it from https://github.com/zestcoin/ZESTCOIN
For build run this:
./autogen.sh

You can see this screenshot for more reference:

After successfully run autogen.sh go for configure, for this
./configure

You can see this screenshot for more reference:

Note:
If you get error named Detected LibreSSL: This is NOT supported, and may break consensus compatibility!
Configure with this command
./configure –with-libressl

After Successfully done with  autogen.sh & configure last go for compile Zestcoin, for this
make
make install  (optional)

You can see this screenshot for more reference:

Note:
Based on your hardware systems configuration it will take 15 min to 45 min.

After successfully compilation run zestd (you can found from it your installed directories src folder)
For this:
./zestd

You can refer this screenshot for more information:

Note:
This can run demmon file of zest coin.
For zest-client file you can run from same directories
./zest-cli

After stop zest demmon file, you can run your compiled Zestcoin wallet, for this execute zest-qt from the compiled directory.
For this:
./zest-qt

You can refer this screenshot for more information:

Now your compiled zest coin wallet is running in your Ubuntu 18.04 LTS
Comment here If you face any problem while compiled Zestcoin.