Quick back of the fag packet calculation says that 4...Kg4 (giving White the Queen) means that mate is 35-ish moves later, but inevitable...
And, yes...the 4 Knights v bishop is very elegant
It's much longer if he doesn't do 4...Nf7+... (Kg4, for example) but then White has a Queen, which is ample material advantage...
In the example cited, if Black doesn't promote the pawns to Knights, then it's over much quicker...
I've tried that...then...
1. Nh5+ Kg6. 1. Ne8+ doesn't work, I don't think.
Then, I can't get any of Nf4+, Bc2+, or Bh5+ to work out well for white...
I figure you have keep checking, otherwise Black has Ba5...