Just a suggestion but if you want to avoid using liquid, you can perform a simple conversion to JSON using an expression and then loop through the result and convert it to your new structure with the loop.

Using the above, I loaded your XML (with the two items) into a string variable and then in the next step, used a Parse json step to turn it into an intermediary JSON structure that preserves the special characters, etc. like you want.
The expression above is ...
json(xml(variables('XML')))
The schema of your Parse json step (to make it easier for you) is ...
{
"properties": {
"ET_KLANTEN_ALL": {
"properties": {
"item": {
"items": {
"properties": {
"KUNNR": {
"type": "string"
},
"NAME1": {
"type": "string"
}
},
"required": [
"KUNNR",
"NAME1"
],
"type": "object"
},
"type": "array"
}
},
"type": "object"
}
},
"type": "object"
}
That will create this JSON ...
{
"ET_KLANTEN_ALL": {
"item": [
{
"KUNNR": "0000071719",
"NAME1": "*STK*Camping 't Strandheem"
},
{
"KUNNR": "xxx",
"NAME1": "Strandshop \"Allaart\""
}
]
}
}
Then all you need to do is loop through each item and append it to an array variable ...

... and finalise the result.

This is the end game ...!

This is the json definition of my answer if you want to load it into your own tenant.
{
"definition": {
"$schema": "https://schema.management.azure.com/providers/Microsoft.Logic/schemas/2016-06-01/workflowdefinition.json#",
"actions": {
"For_each": {
"actions": {
"Append_to_Result": {
"inputs": {
"name": "Afnemers",
"value": {
"AfnemerNaam": "@{items('For_each')?['NAME1']}",
"AfnemerNummer": "@{items('For_each')?['KUNNR']}"
}
},
"runAfter": {},
"type": "AppendToArrayVariable"
}
},
"foreach": "@body('Parse_JSON')?['ET_KLANTEN_ALL']?['item']",
"runAfter": {
"Initialize_Array": [
"Succeeded"
]
},
"type": "Foreach"
},
"Initialize_Array": {
"inputs": {
"variables": [
{
"name": "Afnemers",
"type": "array"
}
]
},
"runAfter": {
"Initialize_Result": [
"Succeeded"
]
},
"type": "InitializeVariable"
},
"Initialize_Result": {
"inputs": {
"variables": [
{
"name": "Result",
"type": "object"
}
]
},
"runAfter": {
"Parse_JSON": [
"Succeeded"
]
},
"type": "InitializeVariable"
},
"Initialize_XML": {
"inputs": {
"variables": [
{
"name": "XML",
"type": "string",
"value": "<ET_KLANTEN_ALL>\n <item>\n <KUNNR>0000071719</KUNNR>\n <NAME1>*STK*Camping 't Strandheem</NAME1>\n </item>\n <item>\n <KUNNR>xxx</KUNNR>\n <NAME1>Strandshop \"Allaart\"</NAME1>\n </item>\n</ET_KLANTEN_ALL>"
}
]
},
"runAfter": {},
"type": "InitializeVariable"
},
"Parse_JSON": {
"inputs": {
"content": "@json(xml(variables('XML')))",
"schema": {
"properties": {
"ET_KLANTEN_ALL": {
"properties": {
"item": {
"items": {
"properties": {
"KUNNR": {
"type": "string"
},
"NAME1": {
"type": "string"
}
},
"required": [
"KUNNR",
"NAME1"
],
"type": "object"
},
"type": "array"
}
},
"type": "object"
}
},
"type": "object"
}
},
"runAfter": {
"Initialize_XML": [
"Succeeded"
]
},
"type": "ParseJson"
},
"Set_Result": {
"inputs": {
"name": "Result",
"value": {
"Afnemers": "@variables('Afnemers')"
}
},
"runAfter": {
"For_each": [
"Succeeded"
]
},
"type": "SetVariable"
}
},
"contentVersion": "1.0.0.0",
"outputs": {},
"parameters": {},
"triggers": {
"Recurrence": {
"evaluatedRecurrence": {
"frequency": "Month",
"interval": 12
},
"recurrence": {
"frequency": "Month",
"interval": 12
},
"type": "Recurrence"
}
}
},
"parameters": {}
}