That is a characteristic of the ZVH. It can be addressed with a different stroke crank and different length rods at a large expense.

The power restriction is the head, not the bottom end by the way. The only advantage is an increase in torque lower down which is a by product of having the longer stroke crank.

The CVH has a shorter stroke which will allow it to rev a lot more freely.

If you compare the power graphs of the 2 engines, you will find that the CVH produces peak power higher up than the ZVH if the spec of the 2 engines is pretty close.