SIP - Add ZEC crypto Synth

Created this post as an alternative place to discuss this SIP instead of the Discord server if anyone feels to do so (first message about it can be found here: Discord)

Here is the SIP: Create sip-add_ZEC_synth.md by MaximilianR · Pull Request #377 · Synthetixio/SIPs · GitHub

If there is anything missing please let me know!