You cannot chain to a Summon, because a Summon does not have a Spell Speed (it is not listed on the Spell Speed chart). When you use cards like "Horn of Heaven", "Trap Hole", "Torrential Tribute", you are not chaining to the Summon. If you are starting a chain (because your opponent responds to your Trap Card), the Trap Card you are using is Step 1 of the chain; the Summon is not a step in the chain.
You can chain to a Flip Effect, Trigger Effect, or Ignition Effect. So you can chain to the Flip Effect of "Man-Eater Bug" (with "Royal Command", "Two-Pronged Attack", etc.) when "Man-Eater Bug" is Flip Summoned. You cannot chain to the Flip Summon itself, but you can chain to the Flip Effect. Likewise you can chain to effects like "Cannon Soldier", "Sanga of the Thunder", etc. (Also note that if "Man-Eater Bug" is flipped by an attack, you cannot chain "Royal Command", etc. to it because you're in the Damage Step).
You cannot chain to a Continuous Effect Monster's effect when it is Summoned.
Which means that...
You cannot chain a Trap Card to the Summon, nor to the effect of "Jinzo". So you cannot chain "Waboku", "Call of the Haunted", etc. to the Summoning (or effect) of "Jinzo." You can, however, use "Solemn Judgment", or "Horn of Heaven" to negate the Summon of "Jinzo" from happening in the first place.