How can you leave two parallel editText inside a ScrollView

defines the property android:orientation="horizontal" to the container of both EditText , in this way they would be shown both horizontally.

Regarding the EditText , so that both elements have the same size you can add the property:

 android:layout_weight="1"

Example:

   <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <EditText
            android:hint="Texto Izquierdo"
            android:layout_weight="1"
            android:layout_width="0dp"
            android:layout_height="wrap_content" />
        <EditText
            android:hint="Texto derecho"
            android:layout_weight="1"
            android:layout_width="0dp"
            android:layout_height="wrap_content" />
    </LinearLayout>

Something important to note is that when you use ScrollView you must have only one container element (child element) which will be traversed by the ScrollView . To achieve what you need, simply add the following to your XML code.

<?xml version="1.0" encoding="utf-8"?>
<ScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal">
            <EditText
                android:inputType="number"
                android:hint="1234"
                android:layout_weight="1"
                android:layout_width="0dp"
                android:layout_height="wrap_content" />
            <EditText
                android:inputType="number"
                android:hint="1234"
                android:layout_weight="1"
                android:layout_width="0dp"
                android:layout_height="wrap_content" />
        </LinearLayout>

        <!--RESTO DE ELEMENTOS A AGREGAR-->

    </LinearLayout>
</ScrollView>

With the value android:orientation="horizontal" in LinearLayout container will cause your EditText to be distributed horizontally.

The values android:layout_weight="1" in each EditText are to achieve that your elements occupy each 50% of the total space on the screen.

The result would be the following: