For easy navigation there are some tools for zooming IN and OUT the map available in the upper toolbar of the WebOffice mobile client.

Zoom Out (-) and Zoom In (+)
It is also possible to jump to the previous/next bookmark

Previous Bookmark (<) and next Bookmark (>)
On larger displays (e.g. tablets) there is additionally a zoom slider in the upper segment of the toolbar allowing a continuous zoom.

Zoom slider in the mobile client
The two finger zoom (multi touch) of some smartphones can also be used. The map can be dragged via a touch into a certain direction (pan). If the mobile client is used in a desktop browser, you can pan via the right mouse button.
Note: Multi touch is supported for Android from version 4.x and iOS.
Note: If the WebOffice mobile client is used on a desktop, a zoom via bounding box is possible with the following shortcuts: Zoom In: Hold Shift + draw a bounding box, Zoom Out: Hold Ctrl + draw a bounding box