Jamal,
There MUST be a ground of some type. What I don't know is if the ground wire for the cap is enclosed or not. I your ZDZ should have a Falkon ignition unit. I went to there site and D/L the manual. (http://www.falkon.cz/English.pdf)

From the manual, their isn't a ground connection. It looks as if it is incorporated into the spark cable and ingnition module so you should make sure the cap is tight on the plug. Use a Tie-wrap or hose clamp to secure the cap to the plug and you should be fine.