Your case is unique in the manner that you have a “Cross License Agreement” with your MaxSea TZ Explorer and your NN3D. (Good news for you) You would need to provide our tech support your MaxSea TZ license number so that the "Chart License Link" can be broken with your old MFD. Your MaxSea TZ Explorer will retain the license(s) to your purchased charts. Once you purchase your new MFD, the TZ Explorer software can be "Linked" to it, and then your new MFD will be granted those same charts. The version of the charts granted, will be the same as you originally purchased.