http://maldomapyy5d5wn7l36mkragw3nk2fgab6tycbjlpsruch7kdninhhid.onion
The reason why t → z exists is because mining funds go to a transparent Bitcoin-like address, then a solo miner or a mining pool sends funds to an anonymous shielded address. Note One might wonder why we can't use anonymous shielded addresses in coinbase payments too, so that the blockchain consists only of z → z transactions.