I suppose Zeal is more interested in wondrous items and architecture. She wants to change society!
I do think claiming gold on the commission is a bit of a jerk move! Zeal isn't doing any work, currently, aside from making some elixir which she is being reimbursed. Zeal getting some fame for her time seems like a good deal. Zeal isn't trying to make money off the plague or Z. She will likely put in some extra work on the formula, but she can accept that.