The only way to produce .ec4 documents is to use Epson Print CD program that can create these files from projects (.ec3). The program can be downloaded from Canon. Unlikely any other program would be capable of this conversion.
Convert Epson Print CD project file to EPSON Print CD document.
We found one software available in the database for this conversion.
Microsoft Windows software - convert ec3 to ec4 on Windows
A program for creating labels for CD/DVDs
Convert from ec3 file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.