The answer depends on the type of license you have. To see details about your license, login and access your Zemax account. In the Licenses table, you will see a License Type column.

Please note: If you have an Ansys license (License numbers starting with 1-) , these are considered Network licenses and have the rights below. 

Individual licenses

Individual licenses are not intended to be shared between colleagues, though they can be transferred from one person to another, such as in the event of staff turnover. Only one person may be the designated end user of the license at any time. Full details about individual license policies can be found in Zemax's Licensing Policies. 

Network licenses

Network licenses are designed to be shared between colleagues. Each person who intends to use the software will be listed as an end user of the license (do this in your Zemax account page). Each end user will also need to install the software on their machine. For more detailed instructions, see How to configure the keyserver and clients for Zemax network licenses. 

Ansys licenses (License numbers starting with 1-) do not use "end users". All license access is controlled from the license server not from the "end user" list. See Configuring Zemax applications to access an Ansys license and Restricting access to an Ansys license on a license server