skill to zoom in and out only with mouse

I believe that you can zoom in and out by using middle(wheel) mouse without skill in 15.7 default configuration .
Usually I also use the function without anything particular setting in 15.7.
Please refer to the following description in the 15.7 product document.

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Middle Mouse Button

Press and hold the middle mouse button while moving the mouse in the direction you want to pan and use the view (zoom) features (see Viewing a Design). If you click the middle mouse button, the system either zooms in or out, based on the direction in which you move the cursor. If you move from top left to bottom right, the display zooms out. If you move from bottom right to top left, the display zooms in. In both cases, a rectangle that depicts the new zoom area displays. You can disable the zoom functionality by setting the environment variable no_dynamic_zoom.

In Windows, for Wheel mouse devices (middle mouse button is a wheel), the middle mouse button must be defined so that the roam function works correctly. Access the Control Panel to open the Mouse Option Control and check the behavior.

The easiest way to zoom in, zoom out, and move across a design display in the UI workspace is by way of the middle mouse button. The button gives you access to all the zoom features available from the menu bar or keyboard commands (except zoom in, which is integrated into zoom points) without the need to make a menu selection or enter a command at the console window prompt. Use of the middle mouse button also enables you to roam or pan across a design.

The zoom function remains active until you click the middle mouse button a second time. (Clicking the left mouse button also takes you out of zoom mode.)

If you prefer not to use the dynamic zoom features, you can disable the functionality by setting the environment variable no_dynamic_zoom in the User Preferences Editor. By setting this variable, middle-button functionality is limited to zooming in or zooming out.

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Hope this helps.
Tomo

I believe that you can zoom in and out by using middle(wheel) mouse without skill in 15.7 default configuration .
Usually I also use the function without anything particular setting in 15.7.
Please refer to the following description in the 15.7 product document.

----------------------
Middle Mouse Button

Press and hold the middle mouse button while moving the mouse in the direction you want to pan and use the view (zoom) features (see Viewing a Design). If you click the middle mouse button, the system either zooms in or out, based on the direction in which you move the cursor. If you move from top left to bottom right, the display zooms out. If you move from bottom right to top left, the display zooms in. In both cases, a rectangle that depicts the new zoom area displays. You can disable the zoom functionality by setting the environment variable no_dynamic_zoom.

In Windows, for Wheel mouse devices (middle mouse button is a wheel), the middle mouse button must be defined so that the roam function works correctly. Access the Control Panel to open the Mouse Option Control and check the behavior.

The easiest way to zoom in, zoom out, and move across a design display in the UI workspace is by way of the middle mouse button. The button gives you access to all the zoom features available from the menu bar or keyboard commands (except zoom in, which is integrated into zoom points) without the need to make a menu selection or enter a command at the console window prompt. Use of the middle mouse button also enables you to roam or pan across a design.

The zoom function remains active until you click the middle mouse button a second time. (Clicking the left mouse button also takes you out of zoom mode.)

If you prefer not to use the dynamic zoom features, you can disable the functionality by setting the environment variable no_dynamic_zoom in the User Preferences Editor. By setting this variable, middle-button functionality is limited to zooming in or zooming out.

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Hope this helps.
Tomo