All of the references cited in my Opening Post date from 2016, long before the BTG project or the BTCZ project existed.
Yes, BTCZ intends to fork on June 15th (and this fork is an upgrade that will not result in a new coin); we’re well aware of this because we’re actively interacting with the BTCZ team, as well as other coin teams in the Equihash space.
Attempts to sow division here are going to fail.
In fact, I’ve been privately encouraging miner developers to try to hit the June 15th target. I have privately stressed that although it may be difficult to meet the June 15th date for BTCZ, it’s well worth trying, and even if they miss that date, BTG will be using the same parameters very soon after, so it’s a great investment of development time. We’re doing our best to encourage development by everyone in the space, for everyone in the space.
Bear in mind that most people who mine, long-term, will probably not use the reference implementation provided by BTG or by BTCZ - we’re all working to encourage the ecosystem of 3rd-party developers.
No, Zhash uses a different internal personalization than Equihash-BTG, although both of our implementations use the <144,5> parameter set for the Equihash algorithm. The personalization is intentional to make it more difficult for attackers to redirect hashpower maliciously; this will be especially important for coins with smaller hashrates.