Although I have seen similar efforts for this task, I had issues using the current eclipse project templates using eclipse jar scripts, so I decided to create a new one applying some of the best practices , and allowing to copy the zkcustomization.jar and customization.jar to your adempiere instalation as well.
1. Copy the zip file to your workspace, and import the eclipse project (custom_Smart_Adempiere361)
2. Update the project references of the new eclipse project, so it depends of your current adempiere project (usually from trunk)
3. Configure your eclipse project location (workspace) and adempiere trunk local installation folder using the buildCustomization.properties file provided.
4. To customized existent java code (swing, compiere, adempiere) just copy your files from the adempiere trunk in the src folder, be careful keeping the file names and packge structure
5. To customized existent java code for web (zk) just copy your files from the adempiere trunk in the srcZK folder, be careful keeping the file names and package structure
6. To customized existent html, css and other source code for ZK (not java) just copy your files from the adempiere trunk in the zkwebui folder, be careful keeping the file names and folders
7. Modify your files as you want
8. take a backup of you current lib/customization.jar and lib/zkcustomization.jar files
9. run the buildCustomization.xml (ant script) as ant build , this script will compile everything, creates the customization.jar and zkcustomization.jar, and it will copy them to the lib folder of your local adempiere.
10. if you want to see the changes, please run your : RUN_setup or RUN_Silentsetup scripts (unix or windows), and restart the server so it can see the changes.