With a proper take off on the first triple and landing in such a way that you are automaticall in proper take off position for the second triple.
Think of shooting pool. Aiming at the 4 ball in the left pocket but at the same time executing the shot so that the white ball is set up for the 5 ball for the right pocket.
Interesting analogy, Joe. To me (a non-skater) it would seem like it would be easier to do a loop as the second jump rather than a toe-pick jump. Because for a loop it seems like you can throw yourself up ugly by pure strength even if your first landing wasn't perfect (like Plushenko's 2-loop at the end of his 4/3/2 combo). But for a toe jump your have to coordinate the pick with what the rest of your body is doing.
(If any skater wants to call me an idiot for this uneducated guess, feel free to fire away, LOL. )
Combining jumps with the loop is much harder cause you have to land with your free leg forward...instead of the natural way which is behind you......
An edge jump is always harder after a jump...and actually two edge jumps are harder to combine then two toe jumps....
Eg :
A) 3sal into 3 loop
or
B) 3 axel into 3 loop
where as
Triple toe triple toe is easier than example A
Triple axel into triple toe is easier than example B
However...there are skaters that are more natural at edge jumps than toe jumps....but rule of thumb is the example I wrote above...
Did you know Kurt Browning had the hardest time with 3lutz...He could do it...but it was a struggle...He only put it in one program I think during his whole career!!!
Sorry Mathman - the loop is more difficult than the toe-pick loop.
The flip and the toe pick flip (salchow) may be more difficult because of the uneasy feeling of the back inside edge. some skaters have trouble with the back inside edge, others don't.
The lutz is the king of the toepick jumps and the toeless lutz is rarely performed. It's the toughest.