Monero uses ring signatures, which as far as I know haven't gotten much traction on Ethereum so far, since gas payments undermine their privacy.
Zcash uses zksnarks, which have advanced considerably since Zcash launched. Ethereum's zkrollups use more recent types of zksnarks.
Stealth addresses "using elliptic curve cryptography were originally introduced in the context of Bitcoin by Peter Todd in 2014," according to Vitalik's post.
Zcash uses zksnarks, which have advanced considerably since Zcash launched. Ethereum's zkrollups use more recent types of zksnarks.
Stealth addresses "using elliptic curve cryptography were originally introduced in the context of Bitcoin by Peter Todd in 2014," according to Vitalik's post.