Zot Defence use to be nearly impossible when you had to use exp instead of zot points.
Now, a broad range of characters have a decent chance...Zot Defence is even more unpredictable than normal Crawl though...
Race choice:
You want something with a good leveling apt because zot abilities come with XL.
Special cases: Trolls are a solid choice if you don't want to die early (you still will
)
Mummies are OK, but it'll take a lot of tries to get started.
Demonspawn can be great, especially demonic guardain.
Other then that, stuff with good aptitudes, like Na, DE, HE, etc.
Class choice:
Summoners are probably the best, Death Knights are really good too.
Berserkers are ok if you want to spam ice statues, since you don't have to worry about freezing cloud killing everything.
Warpers have a nice book. Plus, all Zot Defence characters immediately have cTele.
Generally, something that will keep you alive until you can use zot points.
God choice:
This is probably the most important choice in the new Zot Defence.
Vehumet (for Summoners): MP for collateral kills is the only thing you'll have for a while. Later, the books are amazing.
A Zot Defence Summoner of Vehumet can expect to be spamming imps, canines, and ice beasts for a good portion of the game. Then you're suddenly spamming demonic horde, abominations, ugly things, shadow creatures (these are actually quite good even if it is D:1), and W's.
Yredelemnul: Yred is tailored for Zot Def or something. Animate remains is nice, but Animate Dead is the best. You'll have a huge horde of zombies in no time with Yred. The bonus is that your slaves resist cold, so fill free to use ice statues (I've found that the freezing clouds will still kill zombies over time though) Later, free undead slaves to help defend.
Jiyva: Free Jellies. Zot Def has a bunch of extra items too. You can slimify big things to get acid blobs, death oozes, and azure jellies. The downside is that the jellies will attack your structures if they're in the way of their meal. (That's why you play a Warper with apportation). All G's and J's won't attack anymore.
Sif Muna: Perfect Mummy Summoner god. Probably not as nice as Vehumet if you can't channel indefinitely.
Nemelex Xobeh: Never tried before....but I want to!
Zot points:
I like to put burning bushes on the Orb because they see invisible.
Using a lot of plants is cheap and effective.
Oklob plants will be the base of your defence for a while.
Use ice statues carefully. They have some really great spells, but they can kill you/ your allies.
If you're doing good, save your Zot points. You'll want to have a spending spree when silver statues and orange crystal statues are available. Those two have no drawbacks, and are useful.
The game gets a whole lot easier when you can Zot-port.
I've never used traps, only alarm traps. However, I'm not qualified to say they're entirely useless.
After this point, Zot Defence usually crashes and restarts my character, so I don't really know what >XL20 is like.
Tl;dr: Play a TrDK, a NaWr, a DsSu, or a DESu. Pick Vehumet, Sif, Jiyva, or Yred.
Note: I'm far from a ZD expert, and have never won a ZD game before.