I found some more:
- Cryptopia: https://www.cryptopia.co.nz/ (from https://www.cryptocompare.com/coins/zec/markets)
- BTER.com: https://bter.com/trade/zec_btc
- LZF.com: https://forum.zcashcommunity.com/t/lzf-com-markets-will-include-usd-zec-btc-zec-dash-zec-ltc-zec/4204
- The Rock: https://www.therocktrading.com/en/offers/ZECBTC (https://forum.zcashcommunity.com/t/list-of-exchanges-ready-to-trade-at-28/3254)
- Allcoin.com: https://www.allcoin.com/markets/ZEC-BTC/0/ (https://forum.zcashcommunity.com/t/what-exchanges-are-currently-up-with-zcash/4295)
- TuxExchange: https://tuxexchange.com/ (from https://www.cryptocompare.com/coins/zec/markets)