You can make a map with 8 HOURS of data without a zerolines sd card in the unit. If you want more than that, you will need a zerolines sd card.
You cannot record or change anything on a lakemaster chip. Thus, if the lakes you fish aren't on there, it a lakemaster map is useless to you. You should be able to view a lake list for that map chip on the humminbird website.
You cannot 'update' existing lakemaster maps either. The only thing you CAN do, is create a map on a zerolines card, and overlay that over a lakemaster map on your unit.
If you fish a bunch of unmapped lakes, I would recomment buying a zerolines sd card, and create your own maps with autochart live.
If you fish a bunch of lakes that are already mapped by lakemaster, buy the lakemaster card.