The blob is so big and, well, alien, that it barely even noticed humanity at all before it moved in. Individual zombies dying are about as noticeable to it as losing skin cells would be to us. You would have to do something HUGE to get its attention, like, kill ALL of the zombies at once. Or drop a nuke through a portal to it. Kevin already made it pretty clear in another thread that getting the blob’s attention would be both extremely difficult and suicidal.