- About Zoom lenses
A zoom lens allows the photographer to change how close an image will be within a photograph, without actually having to move closer to it themselves.
There are two different types of zoom lens: Optical, which we will look at here, and digital.
Optical zoom actually changes the focal length (the length between the middle of the lens and its image sensor), increasing the zoom because less of the image hits the image sensor, therefore meaning that the image becomes magnified.
Different optical zoom lenses have different ways of working; for instance some will carry a smooth zoom, allowing the user to stop at any particular place along it, giving what is known as a partial zoom, whereas some will have individual stopping points along the zooms length, therefore providing boundaries to the quantity of zoom positions there are.
This may seem like a disadvantage at first, and most of the time it may be so, but it allows the user to return to the exact point of optical zoom as previously used, which in some scenarios, can be a benefit.
- Block lenses
There is no such thing, it seems, as a block lens. Could it be possible that you are confusing this with blocking up a lens? If so, there are plenty of sites on the internet with easy to follow, step-by-step instructions on how to do so. Perhaps if you add your camera model into a search engine, you may find something more to what it is you are looking for.
For example, this seems a particularly good one: http://ask.metafilter.com/9371/Need-a-new-lens-block . Not only does it explain what a lens block is, but also provides a question and answer service, which may help you should you have any other questions regarding lenses.