Do anybody actually know what the achievements are so that you can aim for them? And how to unlock the equipment such as wheels and different frames etc.?
Ride more, earn experience points, gain levels, get rewards (such as jerseys, wheels, bikes, etc…) 
There is a list of all the unlockables on the fan manual on TitaniumGeek.com
http://www.titaniumgeek.com/cycling/zwift-user-manual-unofficial-running-updates/
It it also details the current achievementsÂ