I assure you that they are most certainly doing both.
The Gen1 worms will need to be made homozygous in order to be able to breed production animals for "Monster Silk".
Meanwhile work will continue on using the zinc fingers to made the necessary changes (deletion of silkworm silk protein genes) to allow the production of pure spider silk. Once that work has been done then those worms will need to be made homozygous. (Each time an animal has genetic modifications done, it needs to be made homozygous.)
I am *guessing* that they are probably starting from "scratch" with the zinc finger work (i.e.: using worms not previously modified with the piggyBac transposon). There are a number of reasons why that would be far preferable:
1) all the added genes would be in exact locations rather than the random ones done by the piggyBac
2) because the piggyBac would not have been involved, no royalties would be owing to ND on ZF modified worms (barring any additional agreements with ND that we haven't been informed of).
3) there would be no non-functional genes remaining in odd places as artifacts from the piggyBac process.
One possibility is that, in order to get a pure spider silk product on the market ASAP, the Gen1 might be modifed using ZFs merely to delete the silkworm silk protein gene(s), and then those animals later replaced by a superior worm produced by using zinc fingers only. I don't think that would save much time at all, nor much money but that depends on the pricing of zinc fingers.
I would be very surprised if the zinc finger work was not being done on worms not previously modified with the piggyBac.
