Update polkadot_stack.md

Add zero network

Author: Noc2

docs/polkadot_stack.md

@@ -120,7 +120,7 @@ In the below sections you can find a list of different layers of the Polkadot St
 |-|-|-
 | Scalable Transactions | [Perun channels](https://github.com/perun-network/perun-polkadot-pallet), [CLI demo of Perun](https://github.com/perun-network/perun-polkadot-demo), [Astar](https://github.com/AstarNetwork/Astar), [Celer](https://github.com/celer-network), [Gunclear](https://github.com/GunClear)| roll-ups, DAG-based consensus mechanisms, side chains |
 | Bridges |  [interBTC](https://github.com/interlay/interbtc), [Ethereum by Centrifuge](https://github.com/centrifuge/), [EOS by Bifrost](https://github.com/bifrost-finance), [POA <> Substrate](https://github.com/paritytech/parity-bridge), [Substrate <> Ethereum DAI Bridge](https://github.com/akropolisio/POC-polkadai-bridge), [Substrate <> Substrate Bridge](https://github.com/paritytech/substrate-bridge-relay), [BTC by ChainX](https://github.com/chainx-org/ChainX), [Cosmos-Substrate bridge](https://github.com/ChorusOne/wormhole-bridge), [Substrate IBC Pallet](https://github.com/octopus-network/substrate-ibc), [Polkadot Ethereum Bridge](https://github.com/Snowfork/polkadot-ethereum), [Darwinia](https://github.com/darwinia-network/darwinia), [Stellar/DeFi Bridge by Pendulum](https://github.com/pendulum-chain/pendulum-prototype), [Filecoindot](https://github.com/ChainSafe/filecoindot) | ZCash |
-| Privacy | [Webb Anon](https://github.com/webb-tools/anon), [ZeroChain](https://github.com/LayerXcom/zero-chain), [pLibra (Phala Network)](https://github.com/phala-network), [Automata Network](https://github.com/automata-network/automata), [zCloak Network](https://github.com/zCloak-Network) |  [Multi-Asset Shielded Pool (MASP)](https://github.com/anoma/masp), [Zkay](https://arxiv.org/pdf/2009.01020.pdf), [Zexe](https://eprint.iacr.org/2018/962.pdf)
+| Privacy | [Webb Anon](https://github.com/webb-tools/anon), [ZeroChain](https://github.com/LayerXcom/zero-chain), [pLibra (Phala Network)](https://github.com/phala-network), [Automata Network](https://github.com/automata-network/automata), [zCloak Network](https://github.com/zCloak-Network), [Zero Network](https://github.com/zero-network) |  [Multi-Asset Shielded Pool (MASP)](https://github.com/anoma/masp), [Zkay](https://arxiv.org/pdf/2009.01020.pdf), [Zexe](https://eprint.iacr.org/2018/962.pdf)
 | ZKP | [ZeroPool](https://github.com/zeropoolnetwork), [Megaclite](https://github.com/patractlabs/megaclite), [zkMega](https://github.com/patractlabs/zkmega), [PLONK for Substrate](https://github.com/AstarNetwork/plonk) |
 | Off-Chain | [substraTEE](https://github.com/scs/substraTEE)
 | DeFi | [Compound Gateway](https://github.com/compound-finance/gateway), [Parallel Finance](https://github.com/parallel-finance/parallel), [PINT](https://github.com/ChainSafe/PINT), [Katal Chain](https://github.com/katalchain), [Laminar Chain](https://github.com/laminar-protocol/laminar-chain), [Acala](https://github.com/AcalaNetwork), [Centrifuge](https://github.com/centrifuge/), [Stafi](https://github.com/stafiprotocol/stafi-node), [Bandot](https://github.com/bandotorg/Bandot), [Definex](https://github.com/y2labs-0sh), [OAX Foundation](https://github.com/OAXFoundation/parrot), [Cybex](https://github.com/alexxuyang/substrate-dex), [Zenlink](https://github.com/zenlinkpro/pallet-zenlink), [Swaps Pallet](https://github.com/lsaether/pallet-swaps), [Polkadex](https://github.com/Polkadex-Substrate/Polkadex/tree/master), [SubDEX](https://github.com/subdarkdex), [HydraDX](https://github.com/galacticcouncil/hack.HydraDX-node), [Substrate Stablecoin](https://github.com/apopiak/stablecoin), [Standard protocol](https://github.com/digitalnativeinc/standard-substrate), [Polkaswap](https://github.com/sora-xor/sora2-network), [Curve AMM](https://github.com/equilibrium-eosdt/equilibrium-curve-amm), [Konomi Network](https://github.com/konomi-network/cumulus/), [Composable Finance](https://github.com/ComposableFi/composable), [Stable Asset](https://github.com/nutsfinance/stable-asset), [Libra Payment](https://github.com/atscaletech/libra), [Mangata](https://github.com/mangata-finance/mangata-node) | DEX with privacy and confidentiality features such as those found in a [dark pool](https://en.wikipedia.org/wiki/Dark_pool)