The Zenith you are looking for are mostly known as System 3. They
used an EFL 110 deg in line CRT. Chromacolor 2 ( CC2 ) sets used a 90 deg
delta gun CRT but it gets confusing !
EFL sets first came out in late 1976 on top of line 17" & 19" using
a CC2 style chassis. By 1979 almost all sets had EFL jugs 13", 19", 23" & 25".
These used the System 3 style chassis. Due to cost EFL was phased out
starting apx 1983. The sets are very common, they sold more color sets
than anyone in the US. Best bet is if you think you found one post the
model number & we can look it up.
73 Zeno
LFOD !