If you want to add Butler and Hayward to the team then you must trade out an equal amount of 2017-18 salary in a Butler trade as you receive.
Your proposition won't work because in order to sign Hayward this summer, Zeller is already gone.
A trade would need to look something like this:
Butler for Bradley, Crowder, Smart at a minimum. Then you can sign Hayward to the max. Basically the only way you can do it is if you trade away 3 core pieces from this years team
That's not quite true. Salaries need to "match", but not exactly. Bradley + BRK #1 probably works, so long as the pick is signed 30 days before the trade.
I get where you are coming from but no. The trade would be made on draft night anyway which means you could use Zeller to make up the salary in your scenario, you don't have to sign the pick first.
Look at it this way. Take the current roster and adjust it to sign Hayward. That is the pool of players you have to trade for Butler. Furthermore, but yes depending on who is in your pool, you will have to match the salary incoming in order to maintain the cap space. Given that it will be a struggle to make enough cap space anyway, it is safe to assume it must be equal.
This is probably a better question to ask post draft lottery as we will have definition over the Brooklyn pick.
The only way this works is to draft and sign whoever Chicago wants on draft night then sign them. Then renounce rights to Green, Amir, Young and KO and don't pick up the Zeller option. Then you have to stash Yabusele another year. This clears the cap space for Hayward.30 days after the pick is signed you trade either Crowder or Bradley plus the signed pick and maybe some future picks for Butler. Assuming we trade Bradley then you have
IT/Rozier/Jackson
Butler/Smart
Hayward/Brown/Nader
Crowder/some vet min or room exception signing
Horford/Zizic
Tha's really the only way this works
That's just not true. Making the trade for Butler on draft night works. It's the entire reason Zeller has his contract structured in this way. What doesn't change is that you would still have to send out matching salary to maintain cap space.
If you do the trade on draft night then you have more flexibility when looking to bring Yab over or keeping Rozier or KO. Now I'm not a fan of this but here is how it could work:
Butler = $17,552,209
Bradley, Crowder, Zeller and Nets 17 = $8,269,663 + $6,286,408 + $8,000,000 = $22,556,071
More importantly for us that is $20,411,271 in 2017-18 salary (assuming 1st pick in the draft). So we would increase our cap space in the summer by $2,859,062. This would put us well into the range to sign a max FA (without the trade we would be roughly $1.8m short). This would mean we could keep Rozier, which would be a plus given who we trade away.
If you sign Hayward first then we
have to move some of these guys out first. When we subsequently make the trade for Butler, we either have to hope the package is of less value (i.e. only one of Crowder/Bradley) or we have to accept an even thinner roster. From a roster perspective it makes more sense to make the trade first.
Edit: Stashing Yab doesn't free up the necessary cap space because it would incur a roster spot charge equivalent to the Min salary. Stashing him would only save $1m which isn't even enough to open up the cap space if we get the 4th overall pick. You have to go further than that.