/summon
doesn't take a a target to summon the mob at, so you'll need to use /execute
, and selectors can't select items by type, so you'll need to use /scoreboard players set
(which can set a score for items with specific NBT data) to set the entity's score first, and then select it based on that scoreboard objective.
First, set up a dummy scoreboard objective that we will use to keep track of items that are iron ingots:
/scoreboard objectives add isIronIngot dummy
Then run this on a clock, to set all dropped iron ingot's isIronIngot
score to 1:
/scoreboard players set @e[type=Item] isIronIngot 1 {Item:{id:"minecraft:iron_ingot"}}
Now, whenever you want to spawn a zombie at the iron ingots, use this command:
/execute @e[score_isIronIngot_min=1] ~ ~ ~ /summon Zombie
Which will make anything with an isIronIngot score of (at least) 1 summon a zombie.
To have this only work with ingots named "Zombie", replace the second command with:
/scoreboard players set @e[type=Item] isIronIngot 1 {Item:{id:"minecraft:iron_ingot",tag:{display:{Name:"Zombie"}}}}
"Adult horses, donkeys, and mules can be tamed, but not zombie horses or skeleton horses. With an empty hand mount the horse repeatedly; when it no longer bucks the player and shows hearts, it is tamed. It is necessary to tame a horse in order to breed it, give it equipment, or ride it for any length of time.
Taming depends on the horse's "temper". Horses begin with a temper of 0 out of 100. When a player is riding the horse, a random number 0–99 is chosen. The horse becomes tame if this number is less than the temper, otherwise the temper is increased by 5 and the player is bucked off. Temper can also be increased by feeding the horse."
http://minecraft.gamepedia.com/Horse
You should however be able to summon a tamed zombie horse by using commands:
/summon EntityHorse ~ ~ ~ {Type:3, Tame:1}
by typing this in chat and sending it, you should have summoned a zombie horse.
Best Answer
There is no single command to accomplish this task in Bedrock Edition 1. However, with that in mind, it can be done with multiple commands.
Note: This answer assumes you're aware of how the summon and ride commands work.
Summoning Jockeys
The summon command can only be used to summon specific jockeys 1 which does not include a zombie jockey:
Note: This quote has been paraphrased for the sake of brevity. For more complete information, please check the wiki article on summoning jockeys.
Break it Down
To accomplish your desired result, you'll need to summon a zombie horse, followed by a zombie, then finally execute a ride command targeted at the two:
1: As of 20 SEP 2021.