As the commenters have pointed out, this isn't trivial.

But, I'm always up for some gcloud-bashing ;-)

Your code sample suggests you want the answer in PowerShell which I don't have and hope you don't mind pointers (what follows is incomplete) in bash:

Does:

• Project ID
• Account name
• Enabled|Disabled
• Email
• Keys
• Creation (timestamp)

Doesn't:

• Role assignments
• Last used (audit logs?)

PROJECTS=$(gcloud projects list --format="value(projectId)")

for PROJECT in ${PROJECTS}
do
  echo "Project: ${PROJECT}"
  # Extracts ACCOUNT_ID, EMAIL (==ACCOUNT_ID@...), DISABLED
  ROBOTS=$(\
    gcloud iam service-accounts list \
    --project=${PROJECT} \
    --format="csvno-heading,email,email.split(\"@\").slice(0),disabled)")
  for ROBOT in ${ROBOTS}
  do
    # Parse results
    IFS=, read ENCODED_NAME EMAIL ACCOUNT_ID DISABLED <<< ${ROBOT}
    NAME=$(echo -e ${ENCODED_NAME} | base64 --decode)
    echo "  Service Account: ${NAME}"
    echo "    Disabled: ${DISABLED}"
    echo "    Email: ${EMAIL}"
    # Keys
    KEYS=$(\
        gcloud iam service-accounts keys list \
        --iam-account=${EMAIL} \
        --project=${PROJECT} \
        --format="value(name.scope(keys))")
    for KEY in ${KEYS}
    do
      echo "    Key: ${KEY}"
    done
    # Creation (Only searches back 30-days!)
    FILTER=""\
"logName=\"projects/${PROJECT}/logs/cloudaudit.googleapis.com%2Factivity\" "\
"resource.type=\"service_account\" "\
"protoPayload.methodName=\"google.iam.admin.v1.CreateServiceAccount\" "\
"protoPayload.request.account_id=\"${ACCOUNT_ID}\" "

    LOG=$(\
        gcloud logging read "${FILTER}" \
        --project=${PROJECT} \
        --format=json \
        --freshness=30d \
        --format="value(timestamp)")
    echo "    Created: ${LOG}"
  done
done

Notes

• Service Account creation times -- IIUC -- can only be obtained through audit logs (CreateServiceAccount[Key]). One challenge with this is having to search back through the project's (entire) history to find these.
• Only user-created Service Accounts are created (during the project's lifetime). Google-maintained account e.g. App Engine will not be found.
• The script searches the logs for each account. This is inefficient and it would be better to search the logs once for all accounts and then merge the results.
• Role assignments is difficult because of inheritance. A naive solution would get the IAM policy for each Project but this is insufficient as it doesn't cover Organizational|Folder permissions nor does it include resource-specific bindings.
• I actually don't know how to grep the logs for last auth times and assume this is available through audit logs
• Apologies for the gnarly base64 encoding of the account's displayName. This is to avoid over-eager parsing of (the majority of) names that include spaces. There's likely a better approach.

The underlying REST method is projects.serviceAccounts.keys.list and the result is a ServiceAccountKey which contains valid[Before|After]Time which are strings in the protobuf Timestamp.

So, I think this needs to either be a string comparison of dates (!) or comparing durations (but I'm unfamiliar with the duration format and how to compare).

You can convert the validAfterTime to a duration, i.e. --filter=validAfterTime.duration() (see duration) and then compare (!) but as Durations

Or construct a date that's within your scope and compare as-is. The following is hacky, please proceed with caution:

CopyPROJECT=...
ACCOUNT=...

PAST=$(date -d "-90 days" +%Y-%m-%dT%H:%M:%SZ)

EMAIL="${ACCOUNT}@${PROJECT}.iam.gserviceaccount.com"

gcloud iam service-accounts keys list \
--iam-account=${EMAIL} \
--project=${PROJECT} \
--filter="validAfterTime<${PAST}"

I think there's a better way to do this!