Shredders are a pain to make, but they’re fairly nice. At medium speeds, they tend to turn zombies into meat without taking much damage.
Military rams are durable enough, and tainted bones useful enough, that shredders probably aren’t worth the bother on most deathmobiles. If you manage to find 30+ blades, though, I would recommend it.
If you ever build a high speed boat, shredders are essential. You hit so many invisible fish cruising through deep water at 50 mph that you boat gets destroyed unless those fish are pureed by shredders.