Zakum doesn't hit hard enough to require washing for, as long as you don't touch body (which as a ranged char you shouldn't anyways because it would stop you from attacking). So you can head there now if you want.
https://royals.ms/forum/threads/zancks-bossing-guide.196246/ I'd recommend starting on HP questing if you haven't already, so that you can eventually do the later bosses when you're high enough level for them.
