Unless you are running a high lift screamer more zddp is not required.
Today's oils have reduced zddp,but they are formulated with other additives to compensate. So the reality is today's oils are better without it.
So forget about zddp. Unless you've got some kind of racing engine from the 60s you don't need it
Ford festiva is essentially a Mazda 121 (Mazda B3 block), and it does not come with flat tappet of any kind.
It is hydraulic-driven, however, with these kinds of hydraulic lash adjusters:
While it does not need any additional ZDDP of any kind, it does benefit from running clean motor oil with proper detergency (to keep the oil passage and within the lash adjuster inside cavity ) clean.
I have one of these in my possession back then, thus the frequent mentioning of B3 blocks in my past signature.
oh and in case you wonder: Mazda B3 block is just a plain, run-of-da-mill mass-produced utilitarian automobile that doesn't call for any boutique motor oil of any kind (no high ZDDP, nadda). Just run of da mill standard grade conventional oil API SN will do justice.
Flat tappets can be solid or the qhydraulic lifter variety
Roller tappets (also called roller cams) have been the norm for decades. They also can be divided into two varieties , solid roller, and the more common hydraulic roller.
Pushrod engines can be of the flat tappet variety, or they might have a roller cam.