They zealously seek you in no good way; nay, they desire to shut you out, that ye may seek them.

Those people are zealous for you, but not in a good way. Instead, they want to isolate you from us, so that you may be zealous for them.

they are zealous for you-- yet not well, but they wish to shut us out, that for them ye may be zealous;

They are not rightly zealous after you, but desire to shut you out [from us], that ye may be zealous after them.