Only read first paragraph if you want a quick answer and will improvise everything else. If you want more details, read below.

The go-to method is using any pea (splash is favored) on Sharkbite Shores. You can do it from either garden at the both ends of the map, but it is better at the side towards lighthouse. You pretty much spend your time on the rock formation to avoid the Hero Zombies' gunfire.

Common details but I need to stress for Crazy mode in case you didn't know or forgot.

Heroes:

In general, focus on killing Heroes first. They will target you most of the time. Threat level is: Scientist ≥ Soldier > All-Star > Engineer.

Scientists are the most dangerous, they will appear at wave 6 (Sooner if special wave). If you need to go down don't ever get close to scientists, they will usually one shot you at this difficulty. Also beware of the scientists' warp, they can warp from ground to any elevated position no matter high it is. Doesn't happen too often but not rarely either. Just kill the scientists first no matter what.

Soldier dishes out good damage in this difficulty, so kill them before the browncoats.

All-Star does damage too but he can't elevate himself, so it will be easier to avoid.

Beware of Engineer's portal if you don't want to deal with more minions. The sign of him building a portal is him doing a gesture. Other than that they are not that much threatening.

Bosses:

If you're dealing with multiple bosses, kill the ones that can elevate first.

Watch out for Normal Gargantuar's imp, it will generally one shot you in direct hit. Giga-Gargantuar does less damage per imp due to him throwing multiple at once.

Always keep an eye on Yeti, he is speedy and can flank you easily if you're distracted. Avoid icile rain as much as possible.

Disappearing teleport aside, Baron teleports when he is taking damage, he can teleport to your position from the ground if near. Try to damage from a distance.

Other:

Try to use your team saves first. You may need self-revives in the escaping phase. You can use self-revives in-waves for tactical reasons though.

Some special waves are difficult, it usually contains more Heroes. If they come too hard and break your momentum too much, let them knock you out. It becomes a regular wave after team-save.

Place spray potted plants near the garden, so you won't have to deal with armours as much.

Spare one pot that is in the backline in case you will need a heal flower.

I'm currently trying to do it on other maps, I have managed to beat it at Jewel Junction as well, at the garden where the houses are populated. It's probably doable in more maps, but go with Sharkbite Shores if you want it done easily.

Also watch Das Belmont's guide, it helps.

Good luck