If you're a super fan and want my suggested reading order based on how my books tie together, here it is:

PRIMAL INSTINCT
CRITICAL INSTINCT
SURVIVAL INSTINCT
CYCLONE (Zac & Anne)
EAGLE (Finn & Charlie)
SHAMROCK (Aiden & Violet)
ANGEL (Gabriel & Jordan)
GHOST (Dorian & Grace)
SHADOW (Heath & Lyn)
ECHO (Cade & Peyton)
PHOENIX (Boy Riley & Girl Riley)
BABY (Baby & Quinn)
CALCULATED RISK (Risk Series)
SECURITY RISK
CONSTANT RISK
RISK EVERYTHING
STORM (Noah & Marilyn)
REDWOOD (Gavin & Lexi)
SCOUT (Wyatt & Nadine)
BLAZE (Kendrick & Neo)
Code Name: ARIES (Ian & Wavy)
Code Name: VIRGO (Sarge & Bronwyn)
Code Name: LIBRA (Landon & Bethany)
Code Name: PISCES (Tristan & Alyse)
Code Name: OUTLAW (Mark & Jenna)
Code Name: GEMINI (Andrew & Tasha)
HERO FOREVER (Ethan & Jess)
HERO UNBOUND (Theo & Eva)
•

OTHER FREE STANDING SERIES

RESTING WARRIOR RANCH
Montana Sanctuary (Connected to: CODE NAME: VIRGO)
Montana Danger
Montana Desire
Montana Mystery
Montana Storm
Montana Freedom
Montana Silence
Montana Rain
•
NEVER TOO LATE FOR LOVE
Collection 1 - HEARTBREAK KEY
Collection 2 - ELLINGTON COVE
Collection 3 - COWBOYS
Collection 4 - HOLIDAY HEROES

OMEGA SECTOR
Stealth
Covert
Conceal
Secret
(Note that although Omega Sector is mentioned in the Zodiac Tactical books, there is no character overlap with the original Omega Sector series)
•
OMEGA SECTOR: CRITICAL RESPONSE 
These 12 books actually make up one long series, even though they're broken into two mini series of 6 books each. They do not overlap with any other series.
Special Forces Savior
Fully Committed
Armored Attraction
Man of Action
Overwhelming Force
Battle Tested
Daddy Defender
Protector's Instinct
Cease Fire
Major Crimes
Armed Response
In the Lawman's Protection
•
SAN ANTONIO SECURITY
The San Antonio Security books do not have any overlap with any other series.
Texas Bodyguard: Luke
Texas Bodyguard: Brax
Texas Bodyguard: Weston
Texas Bodyguard: Chance