FWIW, United's rules for mileage on Z fares posted to UA FF program are:
100% "redeemable" miles, no class of service bonus - That means you earn the miles flown but no 25% bonus for business class that you would earn on full fare (C or D) biz.
150% credit for EQM's - these are the miles that count toward elite levels.
Z fares are not upgradeable to first under any circumstances - all reports are that they are generally quite strict with this. (LH, OTOH, will allow space available upgrades Z to first with a UA certificate. And they give class of service bonus which is posted to the UA account. Go figure, but then, this is the airline industry.

)
Also, all of the fare rules for Z fares I have purchased stated that no further discounts were applicable.