My issue is the value of the Arcanine, and yours is the Zapdos. When we cut both, the remaining trade becomes surprisingly balanced...
My:
NM-M 1st Ed. Sabrina's Gengar $3
NM-M 1st Ed. Pidgeot $?
NM-M CG Blaziken ex $6 (slightly higher than the average auction; lower than the average auction + BiN)
Crap-tastic HL Kyogre ex $X
for
Exc-M 1st Ed Snorlax $?
Exc-M 1st Ed Giovanni's Machamp $2
Exc-M 1st Ed Giovanni's Persian $4
Exc-M 1st Ed Misty's Golduck $3
Slightly above crap-tastic Aerodactyl ex $X
I feel like Snorlax and Pidgeot are comparable exchanges for one-another (inconsistent cards that could both go all sorts of directions in value). Sabrina's Gengar is approximately equal to any one of the other three first editions, and then Blaziken ex CG is equal to the other two.
The difference in values is about as even as we can possibly get. Either way, LMK.