Combining queries in Sanity.io: how to grab data from two different documents with one query

// Specify sets of projections for different content types in an array
content[]{
  _type == 'type1' => {
    // Your selection of fields for type1
  },
  _type == 'type2' => {
    // Your selection of fields for type2
    "url": file.asset->url // Use joins to get data of referenced document
  }
}

*[_type == "collections" && publish == true] {
    heading,
    heroImage,
    slug,
    featured,
  }

*[_type == "marketing_pages" && slug.current == "collections"]{
   seo_title,
   seo_desc,
   page_builder,
   
 }

content[]{
  _type == "collections" && publish == true] => {
    heading,
    heroImage,
    slug,
    featured,
  },
  _type == "marketing_pages" && slug.current == "collections" => {
   seo_title,
   seo_desc,
   page_builder,
  },
}

{
  "first": *[_type == "collections" && publish == true] {
    heading,
    heroImage,
    slug,
    featured
  },
  "second": *[_type == "marketing_pages" && slug.current == "collections"] {
    seo_title,
    seo_desc,
    page_builder
  }
}

content[]{
  _type == "collections" && publish == true] => {
    heading,
    heroImage,
    slug,
    featured,
  },
  _type == "marketing_pages" && slug.current == "collections" => {
   seo_title,
   seo_desc,
   page_builder,
  },
}

{
  "first": *[_type == "collections" && publish == true] {
    heading,
    heroImage,
    slug,
    featured
  },
  "second": *[_type == "marketing_pages" && slug.current == "collections"] {
    seo_title,
    seo_desc,
    page_builder
  }
}