I was sure Zelda was the better game, yet the further I get with HZD the less sure I get. I doubt HZD will beat the 172 hours I spend (or wasted) on Zelda though.
Both games you get OP. Even Lynels went down way too easy in the end and I simply ran by most enemies cause why bother fighting them anymore. I've reached that same stage in HZD, fun to let them fight eachother, yet anything less than the really big ones are no longer interesting to fight myself.
Zelda is bigger and comes with 20 years of nostalgia, yet also with a lot of baggage and expectations. HZD is fresh with a great story. In Zelda I didn't care for the story, nor for most of the side quests. In HZD I'm still doing every side quest I find and enjoy them. Zelda allows for more experimentation with game mechanics and word traversal, HZD lets you experiment more with the combat and has the better UI for that.
They are both awesome, and both much more enjoyable than TW3.