I separated out the buyout into an additional step as I realize some of my wording was misleading.
Part 1
1) Dallas is paying part of Willy Hernangomez's salary in the trade. Dallas will pay $1.1m this year, $0.6m next year. That will count against his cap this year and next.
Part 2
2) After the trade I am buying out Willy Hernangomez, which is the buyout amount ($1.7m) minus any part paid by others ($1.7m). Thus a buyout with no cap hit to my team.
Two separate transactions, trade, then buyout, which are both listed so Billy can easily drop Willy vs. adding to my team and adding what is paid by others, then I submit an additional transaction and Billy has to delete everything he just added.
Trades with subsequent buyouts, drops, contract extensions along with them seem to be fairly normal, but my wording was confusing. Definitely trade with payment on player trading, then buyout by New York Knicks as a buyout by Dallas would have him taking the whole $1.7m cap hit this year.