In that case, if you decide to go with a spawner you can add salt to the zombie flesh to get about 9 times the RF per piece. Salt is just water + a pot so it's trivial to do with aqueous accumulator + cyclic assembler. If you left out any magic mod that lets you convert flesh to leather you can make yogurt instead for over 4x as much RF per flesh (compared to jerky).
Also, have you tried lamps of growth to see if they make farming viable?
I havent gotten lamps yet for Thaumcraft. I just got to building my infusion altar. been working on getting an ender io infrastructure set up. Im sure they will grow crops faster, but i dont think it will make noticeable difference in the trees. But for all i know its been altered as well. The fertilized dirt from Random Things was completely disabled.
I do have cursed earth. Should i use that or a powered spawner for zombies, and what would be best to kill them. i think i have at my disposal, killer joes(requires a liquid though), golems, conveyor or iron spikes.
i could do cursed earth with an attraction obelisk into iron spikes.
With this pack 9 zombie flesh in a crafting table makes 1 leather. but milk isnt easy to get quickly.