This is a pretty good Sunny Day team, there are just a few things that I would suggest changing.
First of all, I feel it's really important for your lead to have Sunny Day, which is why I'm going to suggest changing Azelf's moveset a bit.
Azelf @ Heat Rock
EVs: 252 Atk / 252 Spe / 6 HP
- Stealth Rock
- Sunny Day
On weather teams, it's extremely important for your lead to help support the weather that your team is built around. Since Azelf's main purpose is to set up rocks and sunlight then I feel he shouldn't have any attacking moves other than Explosion, since you don't want him wasting your turns of Sunny Day, as weather teams pretty much rely on weather to win, and you don't want to end up losing a battle because Sunny Day expired a few turns too early.
As for Donphan being one of your Sunny Day users, normally somebody would suggest something else, but I actually think that Donphan could work. If you'd like to replace him though, I would suggest trying to find somebody who's just as bulky as he is. Your Sunny Day users need to have enough defenses to be alive throughout the battle to provide sunlight when needed. Hariyama or Bronzong could work as a replacement for Donphan, you could try either of those out if you want but it's your choice entirely.
That's about it, I'm not too great at rating gimmicky teams but I did my best. You can really use a lot of different stuff for theses types of teams so there aren't many things I can say. Sorry I took so long to rate it, good luck with your team!