I suggest you carefully check exactly what the physicists are saying. People like Tom tend to misunderstand them through wishful thinking. Look beyond Tom - there are much more qualified people able to answer your questions.

Zero point energy is the lowest energy state of a system. By definition no further energy can be extracted from the system.

The closest we come to a theoretical use of zero-point energy involves systems for opposing the Casimir force. Theoretically you might convert zero-point energy from the Casimir force acting on charged plates to mechanical, heat or electrical energy. However, this theoretical conversion process requires more input energy than you get out through the need to mechanically or electrically return the charged plates to the zero-point.

Hence it is theoretically possible to convert the zero-point energy into something usable by applying even more energy from a source that is less usable. Maybe you have a case for increasing the efficiency of some machines but it will never be to the point of over-unity.